The MSDN Checklist: Requirements mention that each computer is a node in a Windows Server Failover Clustering (WSFC) cluster. Most of the online material that shows how to setup AlwaysOn show that WSFC is configured first and then SQL is installed to configure AlwaysOn.
http://msdn.microsoft.com/en-us/library/edbab896-42bb-4d17-8d75-e92ca11f7abb(v=sql.110)
Is it possible to install SQL Server Enterprise Edition on both nodes first, then configure Windows Server Failover Clustering on the nodes and then enable AlwaysOn ?