Workflows with Photos App on macOS

Hi Guys and Gals,
I want to create a better photo workflow for on mac os, I don’t know how to use the media picker or as Sal called it the Media valet. Can someone point me to info on “how to” get photo’s into it so I can choose from the valet in current workflows that would allow it? Maybe there is another way to add easy access?
I am saving something from email media and the export to Photo’s is not working when I choose it in my AppleMail App.

TY in Advance