on the right side of your screen, just above the "suggested tags," you'll find the different things that you can add to your hub (links, photos, text ... an Amazon) Click on the Amazon thing. Then, move down to the bottom of the page and "edit" the amazon section.
Choose "key words"; type in words that match your hub. AMazon will generate a few selections. If you like what they come up with, click Save -- and you're done.