Are those images of the instructors model for you to use as a reference?

Are you expected to use the same workflow? (There are many ways to approach this)

For instance you can..

Google for images of door frames then..

1. start with the door and use its geometry to build the frame and the frame geo to build the walls in a way similar to what you have described above

2. start with a profile of the frame and extrude the frame, then use its geo to build the door and the walls

It is very hard to give you step by step written instructions and I am not sure what your level of skill in maya is so trying to do this quickly a video might leave you as confused as your instructor.