Step 1: Go to the app in "Products" and select the product you want to buy from the
product list
Step 2: Click on "Book"
Step 3: The product and the costs are now displayed, click on "Next" to confirm
Step 4: Now you will be shown your customer data, click on "Next" if it's correct
Step 5: Choose a payment method, confirm the terms and conditions and click on "Purchase"

And you already own your new product!