This is not to be asked here but if you are really seeking for answers... I can say that they are just the same, you just need to find tiles and cliffs for houses then find also some indoor doodads then import them. Lastly, go to your World Editor and create the terrain using the indoor tiles, cliffs and decors like what you are doing when terraining.
You just need the proper resources to do this such as what I said those indoor cliffs, tiles and decors. If you have those check then you can start now and viola!