Click the create game button, select the map, type in what u want it to be named, give your map a password (optional, only if u want it to be private) then click ok. I havent done it for a long time but im pretty sure it goes something like that.
Also depending on how good of an internet connection you have, people may not be able to join your game, or will lag horribly when they DO join, in which case they will probably leave anyway.