I had an idea for Starfinder
 

I thought you could use Real Works to build a Starship, well the interior anyway. Could this be done easy? I am still new to all of this

You can create an "adventure area" topic to hold the main details about the ship. Then perhaps something like "encounter" (I don't remember the real name) for each significant place within the ship.

If your talking a map or deck plans for a spaceship, then you would have to use a mapping program like campaign cartographer. Once you made the map, you could export it to a png or jpeg file and then import that into realm works. You should pay attention to file size and resolution of the exported picture file though, and you may have to play around with export settings to get the best results when importing into Realm Works.