Under Sellers Tools proceed to Profile. Click Profile. In your Profile there is a Billing and Membership section. Simply use the membership drop down choice to choose the appropriate level. If you do not have a credit card on file simply fill in your credit card information and then click the submit or update button at the bottom of the page. Should you wish to change your level in the future simply choose the new level you would like your membership to be and again click the save changes button. Premium and Platinum Memberships are automatically recurring monthly memberships.
Click here for a complete explaination of Membership Levels and Fees