Ok, I give up. And I'm sure I'm blind here.. but I can't figure out how/where to go to start buying/selling cards.
I've uploaded my haves, I added some wants. Can't set prices anywhere.

I understand there's a $10 paypal thing that has to go through, but I can't find where to do that either.

Does buying/selling require a premium account? I don't see anything on the sales pitch page about that.

#halp

At the bottom of this page:

https://deckbox.org/help/selling_cards

Should be a button that allows you to enable your account as a Seller account. If it is absent, you should contact DeckBox.