I tried to draw a graph manually but I kept getting an error message even thoug I did it step by step like the users guide instructions said

This happened to me. I left my calculator open in my bag and accidentally on the 20th function there was a multiply sign, so the calculator would directly output syntax error. Scroll down and check all your function slots are clear.

What happened when you tried going to PlotsOff. Did you actually execute the command?

If you executed that command and cannot graph then for some reason you are feeding lists or matrices as arguments to the functions you want to draw.
By the way are you drawing STATISTICAL GRAPHS or FUNCTION GRAPHS?

If you are drawing statistical graphs and you executed the PlotsOff command, it is normal you will not be able to graph because PlotsOff turns OFF the statistical graphs.

Here are a few things you can do:

If you got the message while trying to draw a graph

1. Press [2nd][Y=] (STAT PLOT)
2. Choose option [4:PlotsOff][ENTER]. Screen displays Done

If message popped up while doing something else that involves lists or matrices, the length of lists may be different, or the dimensions of matrices may not be compatible.

To Clear the lists:

1. Press [2nd][0] (CATALOG)
2. Press [PGRM] (C) to jump to first command that starts with c.
3. Use arrow to scroll down to ClrAllLists, select it [ENTER]
   
4. Calculator displays Done
5. Start the new problem.

To reset the Ram press [2nd][+] (MEM) [7:Reset][1:All Ram][2:Reset]. Press [CLEAR] to erase the Ram Cleared message.

Here is a screen capture to help you pinpoint the location of the error.

A) IF YOU GET AN ERROR MESSAGE,

it might be worthwhile to let us know its contents. If you do get a message ( INVALID DIM) you should turn the statistical plots OFF.
To turn statistical plots off

1. Press [2nd][Y=] to open the (STAT PLOT) menu.
2. Select [4:PlotsOff] and
   
3. Press [ENTER].
4. Calculator displays Done
5. Restart your graphs.
6. Adjust the window dimensions if necessary or use the ZOOM function to have all graphs displayed.
   

B) IF YOU DO NOT GET AN ERROR MESSAGE

Usually as soon as you start entering an expression in the Y= editor screen, the = sign is highlighted to ensure the drawing of a function. However, if you have previously used the Transfm application to draw dynamic graphs, it takes over the graphing functionalities from the native OS and you can only draw a single graph.
The reason is that dynamic graphing needs one or two parameters that can be changed during the graphing process and the graph redrawn with a new value of a parameter, and you end up with a family of curves differing one from the other by the values of one parameters. But since the calculator has space for 10 graphs at most, only one function can be highlighted.

To make a long story short, you must Uninstall the Transfrm application from memory. The procedure will not erase it, just kick it out of memory.

1. Press the [Apps] key.
   
2. Scroll down or up to reach the Transfmapplication.
   
3. Select it and press [ENTER].
   
4. If that application was running you will see a new screen that tells you some thing like
   
   • Transfrm App
   • 1:Uninstall
   • 2:Continue
   
   Press1:Uninstall.
   Graphing functionalities will revert to the native OS
   

Another potential culprit is the Inequalz App. To Uninstall it, do as for the Transfm and select the option that will unload it from memory.

To restore memory on a TI 84 to factory settings follow the directions on pages 108 and 109 of the instructions manual (TI 84 Plus Silver). Otherwise look in the index for RESET MEMORY to get the right page. Be sure you read the precaustions!!!!!!

I found the manual here: http://www.home-electronics.net/USER-GUIDES/21518_DOM_ES_AC_IB.pdf

...with this process you will erase everything....

press "2nd" function and then "Mem" 
then press "F1" and choose "3"
Press ok, and then wait, THAT'S IT!

You must press 2nd then "zoom", then go down to axes, and turn them on. Now your graph will work again.