size variations for t shirt store

I’m pretty new to wordpress and I’m creating a t shirt shop with your paypal plugin. I wanted to create size variations for T-shirts. I saw in the screenshot that I could create color variations but it looked like it created a separate post(item) for the color variation. I wanted to use the same image but have some kind of drop down or way that the customer can select the shirt size they wanted to buy. Thanks, would love to know the solution to this.

🙂