Add different variants to the same store product i.e. size, colour, material, sex.
IMPORTANT. First make sure you have your desired attributes added i.e. size, colour, material, sex. Head to Options>>Store Settings to add these.
Once you've checked your desired attributes are in place, head to Store >> Store Inventory >> click on the desired product>>Add Product Variant.
You can then set the desired attributes for this product. For this T-Shirt we're selecting colour and size.
If you need to add new attributes head to store settings to do so.
Once saved you'll land back on the product. Click 'Add Product Variant' from here.
Now simply enter your desired attributes.
You can setup as many product variants as you require i.e. if you had Small and Medium T-Shirts to sell, you would setup 2 product variants, one for each size.