Pre-existing Users don't show up in console:
Open ADSI Edit from administrative tools
Right click ADSI Edit and Connect to… and click Ok keeping the default values
Browse to the user you want to import to the SBS 2011 Console
Richt click the user, and select Properties
Find the setting msSBSCreationState and set the value to Created
http://www.avantiny.com/adding-an-existing-ad-user-to-the-sbs-2011-console/
tags: sbs2011