If you're just starting out on eBay or if you have a large product count on Shopify that you wish to share with eBay, the publish all option would be the quickest way to go!
However, if you're an existing eBay seller, you will want to first review how to link existing eBay listings to your Shopify products to avoid duplicate listings on eBay.
From the Publish link, select the Review and publish all button.
You'll be directed to a bulk edit page where you may choose to edit any details prior to sending the listings to eBay or simply choose the Save and publish all button to send your products to eBay.
You may also exclude specific listings from the bulk publish by selecting the red X icon.
You may return to the publish all link at any time by visiting Publish in the navigation menu or by accessing Listings, then Ready to list, then select all on the first page of listings and choose the text link to select all products.