Update: I managed to do the ramp using the triangular shape you sent me. Thanks!! The ramp model looked awesome, but couldn't adapt it for my needs.

I also managed to create stairs in Sketchup and import them into SweetHome3D. Still trying to figure out how to create it in such a way that when you go to Modify furniture / Materials, there are separate materials for each part of the stairs (sides, risers etc)