To create other maps, you need to use gates.
Gates can be placed anywhere on your map, the most important part of the linking process is the coordinates and name entered into the dialog box.
Basically, you need to pull up the map you're wanting to link your base map to. My basemap could be something like Farrah Island. And my map I want to link it to could be Terror Caverns. I'd pull up the terror cavers map, place my mouse on where I'd want to APPEAR from the other map, and copy the coordinates in the right hand box.
Then I'd pull up the base map(Farrah), add the gate with the correct name, and enter the coordinates from the linked map(Terror). It basically works the same for linking back to the other map.
If this isn't explained well enough, tell me and I'll elaborate.