Actually like every other addon.
1. You need to add it to your addon collection (The Steam collection must be linked in your server
settings)
2. Subcribe it (you will find it as a .gma file in your Garrys Mod addons folder)
3. Convert the .gma file with a programm like GWTool.exe (It should create a folder)
4. Upload the folder to your server (put it into the addons folder)

How do I use it? I can't find it.