Where do I enter stock for a product that has sizes or colours?

For a Variable product, stock is set for each variant, not for the product as a whole. That is why the Inventory card shows "Stock is set per variant above." instead of a Quantity box.

1. Scroll to the Variants card.
2. Type the stock for each row in the Qty column.
3. Click Save.

The product shows as in stock while at least one active variant has stock. A variant with 0 stock can't be bought.

Keep Track inventory on in the Inventory card so stock goes down as orders come in.