Subscriptions are the recurring services that you have purchased from SiteHost and will appear on your invoice.
Subscribing to Hosting Services
In the My Account module click "List Subscriptions"
Click the 'Add' button
You can choose which hosting plan you wish to apply for, and how many instances of each plan you want to use. More information on each plan is available here: http://www.sitehost.co.nz/hosting/.
Click "Add Subscription"