Capella DARC is a standalone product for Cybersecurity Modelling, based on Capella. Thus, most of the information in the Capella User Manual applies to Capella DARC.
The difference between Capella and Capella DARC are in its user interface preferences: DARC hides many of the menus and actions available in Capella by deactivating several user interface capabilities by default, and by filtering sections in the Activity Explorer.
Capella DARC includes the Capella Cybersecurity Viewpoint