First off, check to see if your shop has a syndication feed or not here: http://www.etsy.com/syndication.php
. It'll either say "active" or "pending." If you're pending, keep checking back till you're in active status. (Of course, Etsy hasn't given any real timeline for getting everyone inserted, they just say it'll be "over the course of the next months")
Then, if you're active, in "your etsy", use the "select all" and "deactivate" buttons at the bottom of each page of your shop, then "select all" again and "activate". And all your items are magically inserted. Just takes once - you don't have to do this for renews or new listings, as that's automatic, but your older listings aren't there yet.