Jay,

I don't want to be rude, but stupid questions get stupid answers.

1 - To make a house with two floors in SH3D, you will have to design the floors side-by-side; you can't make two floors on top of each other.
2 - How to make a map? Explain what you want, because your question is soooooo vague, that it can't be answered. You can import a map as a background picture (see manual), so you can use it to trace the wall.

Good luck,

Hans