Using the attic space

[Stewie]

Thanks for the help with my previous issues with error reports.

How do I access the attic space. I want to put windows in the gable walls.
I am trying to retain the dimensions of the roof space with the roof starting at the top of the exterior walls and rising at a 22 degree pitch in the middle
I've tried doing it by creating a new floor but the walls are too high.
I'm a eager beginner and bumping into a lot of brick walls!!!!!!
Hanging out for a solution
Stewie.