Mapping all those listings can be a chore, but you can do them in bulk.
On your listings page, look for the “Bulk Map” link, click and you will see a list of unmapped listings, matched to a list of website items.
The bulk map looks for the sku or product code in the listing on eBay or Amazon and then matches it with the one for the website. So this relies on you adding the sku or product code into the list. On eBay this is called the custom label field, and on Amazon the product code.
If you sell products with variants, this tool is not available yet
here is a screenshot
