First, be sure to sign into SkyGeek.com so the address book feature will show up in the "Shipping Information" page of checkout.
Simply click the "Account" link at the top-right of SkyGeek.com and fill in your Email Address and Password under the "Sign In" section and click "Sign In." Then click the "Addresses" tab, or go here once logged in.
In the Shipping Address and Billing Address sections of this page, you will be able to either add a new address, or see a link labeled "Edit." From there you will be able to edit and save your address information.