I am trying to update my billing information and it sent me to this site. This site is not telling me what to do.

on ios device go to settings - itunes app stores - click on your apple id - select view apple id- and then enter password. - your billing info is in the account window.

on computer open itunes - go to itunes store - either sign in - or click apple id - view apple id - enter password - billing info under account window