Your first step will be to go to your eBay specific page. You can locate this from the "Listing" dropdown list, which looks like this:
Great! Now from this page, you will want to click the "eBay Actions" button:
Fill out all of the applicable fields for the listing you're creating and save the changes.
If you do not see the product on the Manage Listings page, go back into your eBay specific page and activate the listing, which will push it to the Manage Listings page.
Let us know if you need further assistance.