How to submit a URL? (I know, I know....)

Everywhere seems to lead to a dead-end, and I can't see the point where I can actually make a submission. I know the category I want (Shopping: Publications: Books: Used_and_Rare) but all the information regarding actual submissions seems circuitous, and gets me nowhere. HELP!

http://dmoz.org/Shopping/Publications/Books/Used_and_Rare/ is further subdivided into subcategories for topic areas (if you specialise in some particular subject) and letters. If the site is a general used books shop, or specialises in several subjects, it's listed by the name of the shop - go to the relevant letter category and suggest it there.