Once you login to your customer account, you would just need to choose "My Software" and then you will see all your current software, and to the right of each, your upgrade options.
If you want to upgrade multiple products, first select one as described. As soon as it appears in the DxO Shop Payment window, click on “Continue Shopping” in the upper left corner and you will be back on the homepage of the DxO Shop.
Click on the “Upgrade” button in the upper right to return to the “My Software” section of your customer account. Now select another product for which you want to purchase an upgrade.