Once you've signed up, Joe will take you to the settings page. Helpful instruction will appear next to the spots you need to fill out. First, you'll need to connect your eBay account. Then, you'll need to connect your Amazon. Once that's done, you can choose a plan (optional) and you'll have access to the rest of the website.
eBay Authorization detail:
From JoeLister account settings, click "Authorize with eBay"
This should take you to an eBay page that looks like this, where you should click "I agree." Then you should be all set!