There is definately a template and a how to but I'm having trouble with the template. It has all my old items in it and it hates my new items. I'm wondering if it's the Item ID field that is populated by square.
Anyway.... Here's the link you need to follow the steps even though it feels like you might take an action that you don't want.
https://squareup.com/help/us/en/article/5153-import-items-online
