Step 1: Go to MANAGE EVENT > ATTENDEES > click on ADD NEW ATTENDEE(S)

Step 2: Enter the full name and email of the attendee in the empty boxes. (If you would like the attendee to automatically receive the welcome email turn the welcome email toggle on), make sure the details you entered are correct and click on the ADD ATTENDEE button.

Great job, now you know how to add attendee(s) quickly!