From the Main Menu  go to Inventory, and select  Add stock category. You will go to another page where you must fill in the information about your product. After you fill the required fields (Name, Quantity, Price and Object), go to the Product Details, hence choose Variant.

            Will come new window Properties of the product, select add a new variant / option. From the drop-down menu, select the category that will add (material, color). If material will emerge categories from which you can choose if you want to is another material, press X and they will be removed in the box you can add other materials. On the right you come new window Variant of the product where you need to enter customer and supply costs. Each product can be as different material or color and with different price.