Using the "Modify Process Security" Smart Service .This is the standard way to programmatically change security for a specific active process instance while it is running.

Configuration:

1. Process to Modify: Provide the reference to the current or specific process instance.
2. Security Input: Define which users or groups should have access and at what level (Administrator, Manager, Editor, Viewer, Initiator, or Deny).

Key Note: This service replaces the existing role map for that instance; it does not append to it unless you explicitly include the old groups in the new configuration