Rock Seven provides a web based interface for managing your account which you can access at http://www.rock7.com/register. General information about using this system is here:

Once you've created an account and logged in, you can register your specific Rock BLOCK 9603 modem and enable (purchase) service.

Enabling Service

In addition to the modem hardrware, you will also need to purchase line rental AND credits to use the service.

• Line Rental - Purchased in one month increments, currently £12.00 per month. Needed to communicate with the Iridium satellites. Expires after the purchased time has elapsed. This is a fixed base cost.
• Credits - Needed to send/receive data through the Iridium satellites. These get consumed at a rate of about 1 credit / 50 bytes sent/received. They never expire. Cost varies depending on how many you buy at once, from £0.13 to £0.045 per credit. This is a variable cost.

You can purchase the above through the web based management system once logged in to your account.

More info here: