Hi there,

First, you need to create the different levels and define the height and elevation of each floor. After this you can create each floor, roof, add doors and windows, etc.

The order of the different elements is not important. For example, you can add the topography at the beginning of your project or at the end of it.

Punch, as any program, has a learning curve. The best way to learn the program, IMO, is practice + practice + practice => Read and follow the manual (this is important), see the videos => try to create elements not related with your project, so you will become familiar with the commands and how to develop the different components.

In addition, you will find free tutorials in my Website and Facebook page
Check my galleries to see different images, styles, etc.
If you are interested, this is the link for the V20 eBook for Windows. My eBook includes several tutorials about starting and developing a project, setting floors and elevations, etc.

Hope this helps.