First off, naming conventions are important. They're the primary way that UDK knows what type of map you're playing.
Start your map name with one of the following tags, depending on the intended gameplay type:
Deathmatch, Team Deathmatch, Duel (DM)
Capture the Flag (CTF)
Vehicle Capture the Flag (VCTF)
Warfare (WAR)
So, if you want to make a Warfare map called FirePits , you'd name it
WAR-FirePits.udk
.For this tutorial, we'll create a Deathmatch map. Start by creating a new map or opening an existing map you've created. Save it as
DM-GameplayTest01.udk
in the following folder:C:\UDK\UDK-VersionRelease\UDKGame\Content\Maps
This is the official place where Unreal likes to look for maps, so get into the habit of saving everything there. If you put the map somewhere else, especially if you're streaming or loading separate packages, Unreal won't be able to find it. If you want to make a subfolder, that's fine too.
Build-up your map so that it has at least three rooms...