You can buy a mailbox at any time by clicking on home icon at the top of your control panel.
Scroll down to the Mailbox icon and click on it.
Put in your password to your Photobiz account and click on the gray place order button at the bottom.
You will then need to setup your Mailbox by clicking on the menu icon at the top right of the control panel, then Mailboxes.
From here, click on the set up button.
Fill out the information requested and click on create.
Note: It can take up to 48 hours for your new mailbox to begin working.