If the participant has paid ONLINE via credit card and you want to issue a refund for them, here are the steps:
1. Go to the Registration tab
2. Click the Participants Button
3. Click on the Registered Participant's name you are looking to refund
4. Scroll down to the Payments & Refunds section and Click 'Online Refund' in the actions column of their payment
5. Enter a comment and click 'Initiate'
Once the refund is issued, it should also appear as refunded in your league's Stripe account.