Gable Roof

I can't quite get the hang of specifying a gable roof and find the help part confusing. What is the procedure?

Also I am in Scotland and was wondering if there was a way of adding local suppliers products to the library. Am enjoying discovering the programme.

Thanks
Nige

Article Number 359: How to automatically build the basic roof styles

Article Number 888: How to import a 3D symbol from an outside source

Thanks for reply, great help.
Nige