When merging help systems, you must designate one project as the Master or Host project. All other projects are then Subordinate or Slave projects. WebHelp can be merged using the New Merged Project function found on the TOC tab.
Open the master project and click the New Merged Project icon on the TOC toolbar.
Browse and select the MPJ
file of the subordinate WebHelp project.
An icon is added to the Master TOC.
Generate and publish the
Master project to a new location.
This action creates a mergedProjects folder in the published location.
Open the Subordinate project
and publish it to the merged
Below is an example of the new add-on merge module for WebHelp.

See Also:
Publishing sub-projects into a Master WebHelp system
Limitations when merging WebHelp