put them in add ons and enable them?Of course on LAN the computer hosting is the one that needs the add ons.
There's a map that I downloaded that I want to use, I have zipped and unzipped with all the textures and map files in both, and it still doesn't show up in the map list in-game.
He means being able to use the maps downloaded after joining a server, not off the forums: this is impossible unless you write your own .mis file for it or use the Mission Editor to get the terrain file and save the map again.