Put those files wherever you usually put your mods, and in whatever folder organisation you use. Its the files in the skins folder that you want. Extract the mod files from the provided BD64 Zandronum installation. Korell: The same way you get Brutal Doom working, really, as it is just a mod. I actually created myself another PK3 that just customises the campaign selection menu to hide the multiplayer. Note that I've not loaded the STAnnouncerPack as the multiplayer doesn't seem to work with GZDoom and it has no bots for botmatch either. The launch GZDoom using the Doom 2 IWAD (doom2.wad) and with the three BD64 mod files loaded in this order:

The same way you get Brutal Doom working, really, as it is just a mod. I am asking because I don't use Zandronum and would prefer to use my usual. It uses Zandronum by default but the readme says it can run via GZ Doom. Darkredshift: I posted about this on the 'Brutal Doom 64 release imminent' topic but I've posted it here too just in case no-one sees it.

How to play brutal doom multiplayer