1. Navigate to Fundraising > TeamRaiser
  2. Next to the TeamRaiser in question click "Manage"
  3. Search for the participant and navigate to their record
  4. Click on "Enter Offline Gift" and record the gift. You will have the option to create a new constituent record for the donor, or use an existing record. 
(If they are associated to a team, the gift will automatically be attributed to the team)