How to add new variant to existing listing?

Hi!

I’m just getting into Amazon FBA and am trying to list a product (decorative wall art sign) by its UPC. But, the UPC already used on Amazon is the same wall sign but different style (different design and text). I tried copying the existing listing and adding a variation, but it won’t let me add different details about my product. It seems as if I am restricted to keeping the existing product title and existing product variations (which don’t match my product).

From what I can gather online, I will need to purchase a UPC, use that to get an Amazon FNSKU, then apply labels over the existing UPC.

Is this the correct process or is there a better way?

Thanks in advance!