Go into config.yaml and change the cooppassword to whatever your want it to be, and set EldenRingPath to the path to the eldenring game directory it should look like this
C:\steam\steamapps\common\eldenring\game for windows or if your on linux I really hope you know the path to it.
Make sure your in the ELDENRING\game directory or it will not work
Here's another example:
EldenRingPath: E:\SteamLibrary\steamapps\common\ELDEN RING\Game
If it doesnt look like this it will not work