Docs:Run Level
From Mod Wiki
After compressing the level with textures you need to copy compressed db
file in the directory of game which is used for keeping multiplayer levels - "C:\Program Files\Deep Silver\S.T.A.L.K.E.R. - Clear Sky\mp"
Start "S.T.A.L.K.E.R. - Clear Sky"
and in the list with multiplayer maps we can see our new map.