Launch the application and click on product definitions to see a list of existing product templates:
The section labelled 1 shows all available properties that can be assigned to the new product template or its variant. If there are not enough suitable properties, you can create one by clicking on propertied definition on the left under views.
The section labelled 2 is where you assigned regular fields or properties for the products to, such as Brand, Base Price, Material
The section labelled 3 is where you assign variants fields/properties to such as size, color, length, height, width.When done, click save and close and your new product template will appear on the list.
While in Catalog Manager, click on Refresh to get the new template synchronized.
After updating data templates, your new product template will be synchronized into Sitecore and ready for use in creating products on the site.