If the participant has their own constituent record:
- Go to the Participants tab of an event
- Double-click the participant name that is not showing in bold
- Click the '...' button in the Registrant field
- Click the binoculars button beside the Last Name field
- Search for the participant's constituent record
- Click OK and save the participant record
If the participant does not have their own constituent record, you can create a Constituent record for them.