Compiling is quite simple. To do this, Fragsurf uses Unity's Asset Bundle feature to build a scene into a bundle that can then be loaded in-game. All you need to do is open the scene you wish to compile, go to Fragsurf -> Build Utility, and hit Build. There are two things to note when building your map:
To make your map visible in-game under a certain category, move it to the Fragsurf content folder
Fragsurf_Data/StreamingAssets/Content/Maps and make sure one of the following prefixes is included in the file name:
After compiling your map to the Fragsurf map folder for the first time, restart the game for it to appear in the main menu.