Right click on the DESlock+ Icon in the Notification Area (also known as the Task Bar). Select About DESlock+ from the menu. 

The DESlock+ About window will be displayed. The installed version number of DESlock+ is displayed in the top left hand corner (circled in red below).

Managed users

For a managed user, you can run a report to discover the installed version of DESlock+ on all client machines, for information on how to do this, see the knowledgebase article Discovering the installed DESlock+ Client version from the Enterprise Server