How do I add multiple sizes and quantity to each size? TY

[gizmo*s_collectables1]

How do I add multiple sizes and quantity to each size?

[nobody*s_perfect]

To set up a listing with the variations format, you have to (1) set up a fixed price listing, not auction format; and (2 use the Advanced version of the listing form (AKA the business tool) not the simple/quick version.

The "Variations" option isn't available in every category:

http://pages.ebay.com/help/sell/listing-variations.html
https://pages.ebay.com/sellerinformation/sellingresources/multiplevariationslist.html