When you install the Revit software, the complete set of Help files is stored locally on the target computer.
By default, when you access Help from the software, Revit detects whether you can connect to the Internet, and automatically displays the appropriate Help.
If you prefer to always access the locally stored Help files (offline Help) instead of WikiHelp, edit the Revit.ini file and, in the Documentation section, change the value of UseHelpServer to 0 (zero).
[Documentation] UseHelpServer=0
If you want to use a copy of Help stored in another location, add the setting HelpFileLocation, and specify the path or URL to the Help system.
[Documentation] UseHelpServer=0 HelpFileLocation="M:\RevitResources\Help\en-US\WBH"
After saving changes to Revit.ini, restart Revit to see the results.