If your product features variations and you wish to include Size or Color, simply click on the Add Variants option located at the bottom when creating a new product or modifying existing product details.
To incorporate Size, select the Add Size button. Input the size name, its MRP, and selling price. Should you need to remove any size, click on the Delete button to eliminate it.
Once done, click on Save and continue button at the bottom. Your variant details will be added to the product.