How do i get a size option to appear for the tshirts I'm looking to sell?

[stle-4904]

How do i get a size option to appear for the tshirts I'm looking to sell? I've set up a page with some t-shirts I've printed and can't see how to get the size option to show up for customers.

[twyngwyn]

https://www.ebay.com.au/help/selling/listings/creating-managing-listings/creating-listings-variation...