This is the first screen you will see after you choose your ring tone from the widget. You will be able to hear the ring tone before you purchase it. Typical price for a ring tone is US $1.99 but may vary, you will see the total before you commit.
Below is the next screen where you specify your country, phone system and type of phone.
Below is the screen where you enter your phone number. The next screen (not shown) will provide you with detailed instructions on how to load the ring tone properly.