The appData.cfg file can generally be found at:
C:\Users\yourUserName\AppData\Roaming\psychopy3
I sometimes have an issue with PsychoPy not creating icons on my desktop so I edit a copy of an existing one. Here is what I have in mine:
Target: "C:\Program Files\PsychoPy\pythonw.exe" "C:\Program Files\PsychoPy\Lib\site-packages\psychopy\app\psychopyApp.py" --builder
Start in: "C:\Program Files\PsychoPy"