The search function in Revit Help doesn't really work. This is a known problem with AutoDesk's on-line Help system.
By default Revit uses the on-line help, but there is a local version of the help system (although possibly not as up to date as the on-line version). Changing Revit settings so Help uses the local files improves search functionality, and as a bonus works much faster.
Switch between local and online help documentation for Revit 2011 products
Issue
You would like to know if you can set the default location for Revit 2011 help documentation because searching the User Guide produces no results.
Solution
There are two options for specifying where Revit 2011 products will look for help documentation. You can customize the location by adding the following information to the Revit.ini file.
The Revit.ini file is located in the following folder:
C:\Program Files\Autodesk\Revit Architecture 2011\Program
If they do not exist add the following 3 lines to the bottom of the Revit.ini file:
[Documentation]
UseHelpServer=1
HelpBrowser=0
To specify online help documentation use UseHelpServer=1
To specify local help documentation use UseHelpServer=0
Additionally you can further customize which web browser help documentation will launch with:
To specify the system default browser use HelpBrowser=0
To specify Microsoft Internet Explorer use HelpBrowser=1