You go to your profile and click "Edit signature" and under the text box there will be 3 drop down lists, where you can choose what to show. You can show lists (like what's in the picture you posted), reviews, albums, and classifieds. (Those are what I know of -- not sure if there are any other things you can show off.)
The "Hide 'My Stuff' in signatures" is if you don't want to see the things in signatures. Helpful for folks who have slower connections or just don't want the distractions.