If you press "Add commands to existing product", then you will be asked to choose between the products available on the Ipad. When you select a product, then the commands for the product you are importing will be added to the selected product instead of creating a new product. This could be usefull if you at some point find the commands you are missing for a local product. Then you just create an "Temp Product" TPF file with those commands and import to the local product.
After pressing "Save and Close", then the product should be available under "On this iPad" in the Main Menu, or the commands added to the already existing product.
Then it's just a matter of testing the product.
When the product has been tested, please upload the product to the server for other people to use. How to upload to the server is described here.