Many say its not possible but it is haha , when registering, put your phone as unlisted , the manufacturer as unlisted , and the carrier as unlisted . Then when verifying your phone number, it asks you for a mobile email . Put :
(your number)@mblpix.com

If it asks for something like your model and manufacturer , write "boost 2300"

After that change your downloading options ( in my zoo ) to multimedia and it should work fine . Did this help ?
YOU STILL CANT SAVE RINGTONES THOUGH SORRY :/