http://www.adobe.com/products/creativecloud/faq.html#account-managemen t
"If I decide I would like to upgrade to an Adobe Creative Cloud complete membership rather than continue a single-app membership, how do I do that?
You can upgrade your single-app membership to a Creative Cloud complete membership by logging in to www.creativecloud.com, going to the My Account page, and simply walking through the steps to upgrade. You will be given a partial refund on the remaining amount due on your existing membership."