All you have to do is log into your account and go to Settings ⇒ Public Profile ⇒ Settings & Privacy.
You will find an option called: "Displaying my Services ID" and you will be asked to add the minimum amount a member must have in his account to be considered premium ($1.00, $5.00, etc.). Do not forget to save the changes.
¡Please note that the Skype ID is required for the members to be able to contact you on Skype and have calls with you!