Priority is setup for the Building Materials that you use for a composite. So you need to change them in the Building Materials settings (if you wish to change them).
It looks like you are using an older version of ArchiCAD (at least before version 20), there might still be tutorials to be found for your version online, if Graphisoft keeps an archive of those. I would suggest having a look at those, as they take you through the most basic functions.
Erwin Edel, Project Lead, Leloup Architecten
www.leloup.nlArchiCAD 9-26NED FULL
Windows 10 Pro
Adobe Design Premium CS5