Is there an explanation about how to use Resources, for the menu, Head, Footer part.

Their all the same thing. CC has given multiple areas to get at the resources to add your needed support directories and files.

I usually open Resources at the start of any of my projects and create an img (images), custom (custom css and scripts), and files (storage and retrieval of stuff). Then I locate and grab all the stuff I think I'm going to use on the project to start with, and the nice thing is you can just keep grabbing and adding things to your resources as you need them.
Once your done or at a testing point - you can just export your project and publish / ftp it up to your server and everything is all ready to go
Really nice system. It reminds me of a Blender project system. Love it.