I install new oil sensor switch and change oil and filter. but still dont help

Most, but not all car engines have an oil pressure switch or sensor and it tends to be located mostly in the oil filter head or screwed into the main oil gallery but I have seen them fitted to the cylinder head oil gallery.
A few engines also have a switch to signal oil filter blockage and others a sensor to monitor oil temperature and there are others with oil level sensors.

It is a good idea to check the vehicle handbook so to be certain what sort of switch or sensor you are seeking.

It is really hard to get to, but really easy to change.

Unhook the battery cable so you don't blow the new one when you install it. Depending on the location, you may have to remove the oil filter to be able to access the sensor.

Unplug the wire off the end of the sensor, slip a socket onto the old sensor, and unscrew it like you would a spark plug. Before you out the new sensor in make sure it has Teflon tape on the threads. I always a little more than what comes with it.

Screw in the new sensor "hand tight" - then 1/4 to 1/2 turn past hand tight; do not over tighten. Plug the wire on the end. If you removed the oil filter, replace it with new one. Last step - replace the battery cable.

The oil pressure switch should be by the oil filter. You will need a socket 1 1/8 ,I believe is the correct size.

Disconnect the oil pressure sensor electrical connector
Remove the oil pressure sensor and washer
remove the oil filter and o-ring (you may have to use a flat head screwdriver to get the filter out)replace the filter and o-ring assembly.
apply sealant to the threads of the oil pressure sensor (I would replace the sensor
while you at this)
install the pressure sensor and washer to 15 lb ft.
reconnect the oil pressure sensor.

well let me see you have 4.6L engine you need 7.5 quarts of oil with new oil filter.to do the oil change you need large drain pan and oil filter wrench and a metric wrench to remove oil drain plug you need a funnel also.you need first start engine let it run for 5 minutes to warm up thin out the oil so it will flow better.once engine warm up.turn off the engine.open you hood.now safely raise support vechicle on jack stands make sure vechicle parked on solid level ground.place large drain pan under oil pan remove oil drain plug you need a 15m wrench remove drain plug let all old oil drain out until you see slow drip then reinstall oil drain plug dont over tighten drain bolt.then place drain pan under the oil filter then remove oil filter using oil filter wrench or large channel lock pliers.once you remove oil filter wipe oil filter seal surface with clean paper towel.take new oil filter add oil to new filter then install new oil filter hand tight take filter wrench turn oil filter one half more turn dont over tighten will damage oil filter seal.make sure oil pan drain plug is in place. then lower vechicle. remove oil filler cap on the valve cover add new oil to the engine using a funnel to keep from spilling oil all over the valve cover and exhaust manifold.add all 7.5 quarts to oil crank case wait until oil settle down in crank case check oil dip stick oil level should be at the full mark on oil dip stick.dont over fill crank case.once you finished oil level correct crank engine check for oil leaks at oil filter and oil drain plug. if engine running okay you see no oil warning lights you ready wheel and deal.

If you don't repair the water pump you will be walking, A used motor runs around $500-$750 and the labor to put in the engine is $500-$1000 so you dicide if you want to spend a couple hundred now or $1500 later, I would fix the water pump and install a new thermostat and coolant.
As for the oil light= check that the wire connector is attached to the oil pressure sensor located by the oil filter, replace if the wiring is good, now if it is still on, put an oil pressure gauge on where the sensor is installed and check to make sure the oil pump is producing pressure

OIL PRESSURE SWITCH ON LOWER SIDE OF ENGINE NEXT TO THE OIL FILTER.BOTH ARE ON THE SAME OIL CHANNEL IN CYLINDER BLOCK.ALL YOU HAVE DO TO REMOVE IT.IS DISCONNECT OIL PRESSURE SWITCH ELECTRICAL CONNECTOR.THEN USE A OIL PRESSURE SWITCH SOCKET WITH A RARCHET WRENCH AND EXTENSION..YOU CAN BUY SOCKET AT ANY AUTO PART STORES.REMOVE OIL PRESSURE SWITCH. WHEN INSTALLING NEW ONE MAKE SURE THREADS HAS SOME KIND OF SEALER LIKE TEFLON TAPE CAN BE USED ON NEW OIL PRESSURE SWITCH IF IT DONT HAVE NO SEALER ON THREADS. WHEN YOU GET NEW ONE IN PLACE CRANK VECHICLE CHECK FOR LEAKS.

on the top left side of engine near the distributor/high voltage switch sorry dont have picture

Best would be is to measure the oil pressure out put.
Sometimes the oil filter could be the culprit.
Was the oil warning light staying 'on; prior to the oil and filter change?..If not thn the first thing to check is to replace the oil filter ..its better to install the 'original' one .
Hope this helps!

It's a direct shot....

Removal & Installation

1. Disconnect the negative battery cable. Raise and safely support the vehicle.
   
2. Drain the engine oil into a suitable container.
   
   1. Remove the transaxle converter cover.
      
3. For 1986-90 vehicles, remove the starter motor from the vehicle, as outlined in Section 2.
   
4. Remove the oil filter.
   
5. If equipped, disconnect the oil level sensor.
   
6. For 1996-99 vehicles, remove the oil level sensor. On these vehicles, the oil level sensor must be removed prior to removing the pan. If the pan is removed first, damage to the sensor may occur.
   
7. Remove the oil pan-to-engine bolts and the oil pan. Remove and discard the oil pan gasket. The formed rubber oil pan gasket cannot be reused.
   
8. If necessary, remove the oil pump pipe and screen.
   
9. Thoroughly clean the gasket mounting surfaces.
   

To install:

1. If removed, install the oil pump pipe and screen. Secure with the retaining bolt(s) and tighten to 89 inch lbs. (10 Nm).
   
2. Place a new formed rubber gasket in the oil pan flange.
   
3. Position the oil pan and secure with the oil pan-to-engine bolts. Tighten the bolts to 124 inch lbs. (14 Nm). Do NOT overtighten the bolts, as this will damage the oil pan, causing a leak.
   
4. For 1986-90 vehicles, install the starter motor and transaxle converter cover.
   
5. Install a new oil filter.
   
6. For 1996-99 vehicles, install the oil level sensor.
   
7. If equipped, connect the low oil level sensor wire.
   
8. Carefully lower the vehicle.
   

WARNING Operating the engine without the proper amount and type of engine oil will result in severe engine damage.

1. Fill the crankcase with the proper type and amount of engine oil.
   
2. Connect the negative battery cable, then start the engine and check for leaks. Check the oil level and add if necessary.