First you need to install the UML2 feature from eclipse.org:
http://download.eclipse.org/modeling/mdt/updates/releases/
The Xpand uml2adapter is available from the Xpand update site:
http://download.eclipse.org/modeling/m2t/updates/releases/
(Go to the home page of the project and find the current location if either of the sites do not work)
Restart your Eclipse workbench when Eclipse asks you to do so.