First make sure that the current input Source is set to TV to see the option for scanning for channels. There is a Source button on the front of the TV. (It's on the right side as you look at the front of the TV.) The Source button on the original remote is on the left side below the number keys.There are two RF (coaxial) cable inputs near the VGA port on the back of the TV. The digital RF signal needs to go to the port above the VGA port.
To scan for analog channels, press the Menu button. Then navigate to the TV setup option with the Up/Down arrows. Press OK to enter the menu. You can use either the Auto search or the Manual search. However, the Auto will be faster. You can set your country or leave it to Auto. Navigate to Start and press OK for the Auto-scan. There is a DTV menu button above the Volume + button on the remote. Use this menu and look for the Installation section to scan for channels. Again there is an Auto or Manual option.
ManualsLib has the manual for the Viewsonic N3246W here: https://www.manualslib.com/manual/306714/Viewsonic-N3246w.html
. See page 23 for the start of the analog TV channel scan information. See page 30 for the digital TV scan.
I hope this helps.
(For any channel provided by a set-top box, you will not be able to use the TV to store the channel lists.)