A universal remote comes with all the commands for all the TVs it can control already programmed into it. The code you enter is to tell the remote to use these specific commands that will operate your TV. Since there are many different types of remotes, you need to know the model of the remote to look up remotes codes as well as the TV brand. Based off the link to GE remotes you gave me, if your remote uses 4 digit codes then you would try 0062, 0004, 0009, 0135, 0189, 0183, 1141, 0227, 0456, 0008, 0068, 0075, 0141, and 0161. If its a 3 digit code try 586 or 666 but I think these are a little dated.
To enter these codes, first turn the TV on. Hold code search/setup until the little red light blinks. Press and release the TV button. Enter one of the codes and after the red light blinks off, try to turn the TV off and on.
If none of the 16 codes provided work, you can try searching through preprogrammed commands one at a time. Turn the TV on. Hold code search/setup until the red light turns red. Press and release the TV button. Hit power and see if the TV turns off. If it does not turn off wait 2 seconds and hit it again. Every time you hit power it cycles to another set of commands already programmed in the remote. There are likely over a hundred sets of commands so this method requires patience.
GE also includes this contact information for assistance:
For further assistance please contact our Customer Information Center at 1-800-654-8483 option 4 or firstname.lastname@example.org.