2. Play Final Doom & Master Levels - MadDeCoDeR/Classic-RBDOOM-3-BFG GitHub Wiki

Final Doom

you must legally own the wads (either acquired from retail, steam or GOG)

and then copy the two WADs on the /path/to/Doom3BFG/base/wads.

Master Levels

you must legally own the wads (either acquired from retail, steam or GOG)

1. make a folder named "master" on /path/to/Doom3BFG/base/wads

2. copy all the 20 wad files on the folder you made in the previous step.