This should help for brushes:
I doubt that you can save custom shapes.
This video is very good. Towards the end, she gets in to loading brushes:
In Windows, put your downloaded shape files (which need to have the .csh file extension) in C:\Program Files [Program Files (x86) if you have a 64-bit system]\Adobe\Photoshop Elements 11\Presets\Styles. On a Mac, it’s Applications→Adobe Photoshop Elements 11→Support Files>Presets→Styles. The shapes will appear in the Shape Picker in their own category with the same name as the .csh file.
It is definitely possible to add shapes via styles. Shapes are .CSH. styles are .ASL.