I’m also a noob, but I try to help:
Be sure to setup your keyboard in the raspi-config (Emulationstation->RetroPie->Raspi-Config), if it’s not an international one. I use a Quertz-keyboard, so it had to be changed.
Since I only use my keyboard for setup or ScummVM games, I mapped it like this:
Just skip the buttons you don’t need by pressing any button for a long time. If your assigned “A”-Button doesn’t work try the “B”-Button instead. Perhaps they got switched during the process.