How do I add Printful inventory to my store without SKU?

Hi. I am new to Shopify and have gotten to the point where I am trying to add Inventory. I am using Printful. When asked “Inventory Managed by” I selected printful. However, when I try to submit it says I can’t submit without a SKU and that the SKU much match Printful’s product SKU. However, Printful doesn’t use SKUs. So it is is not allowing me to proceed. Does this mean I have to say “inventory managed by Shopify” (as that doesn’t require a SKU)? If so, how will that affect orders that come in? Will Printful not be able to fulfil the order since it will say inventory managed by shopify and does that mean I will have to MANUALLY enter every order that comes in into Printful?

I simply want customers to be able to go to my Shopify store, purchase what they want and Printful gets the order to fulfill it. This shouldn’t be this complicated and makes me rethink choosing shopify the more and more roadblock I run into with adding inventory. Ugghh.