Go to the Releases tab for the latest (zipped-up) Stable or Development Snapshot pk3. Otherwise these files must be downloaded, the github-specific files deleted, and then using 7zip or another archive tool, zipped up and saved with the .pk3 extension to get the very latest build of the project.
I recommend using a Doom launcher program to place all the files in the correct order for play. Else you will have to write a .bat file or select (in correct order), drag, and drop them all onto your port's executable.
- Doom.wad or Doom2.wad
- any map-only wads
- brutalv21.x.x.pk3
- music wads and any files that are not going to rewrite files already modified by the brutalv21.x.x.pk3 unless specificaly developed with the brutalv21 in-mind or else you risk conflicts and unforseen errors.