Manage your participants by following these steps:
Select the event in your Admin Dashboard
Choose the Participants tab
Find the participant
Click the dots in the far right column for that participant
Choose between Copy Join Code, Resend confirmation email, and Block User
Copy Join Code will copy that participant's Unique Join Code to your clipboard
Resend confirmation email will resend the confirmation email to that user
Block User will make this participant unable to join your event
You can find more tips on using Sequel.io Registration here