Go to the
Tutorials Page on this site and find the one on building a house. The concepts would likely be the same to create an interior space as well.
Also, if this is your first 3D program, you may need to view other tutorials in that section just to get a basic vocabulary on 3D programs. Those are the basics you must have to start.
Knowing what a vertice is, what a surface is, what a normal is, what a primitive is, and so on... you just have to know things like that to even have a discussion! Good luck!