If you are not using an exernal directory service, you can add participants from Process Administrator.
The participant is added to the organization, and the Edit Participant pane appears, with the settings for the just-entered participant.
After you have added the participant, you may want to assign roles or groups to the participant, you may need to define an absence period, or you may need to change the participant's password. You can access these settings from the Advanced Properties section of the Edit Participant pane.