The option to set-up WiFi is in the Retropie menu. So once emulationstation loads up and you see the emulators, scroll over and select Retropie. Once you open that you should see the option to setup WiFi.
UPDATE to the threads topic:
My Pi successfully connected to my WiFi ONCE out of probably 200 times. No clue what could be causing the issues. But there’s nothing I can do at this point to troubleshoot the problem.
My newest problems are there’s some noticeable lag with my BT PS3 controller input (tested in SNES), and for some reason snes9x-next doesn’t pick up my joypad (BT PS3 controller). Still having fun figuring this stuff out despite it stressing me out.