You would need access to the email address used to purchase the event ticket.
Option 1 - Find the ticket purchase confirmation email that was sent while purchasing the ticket in your inbox. Click the 'Enter event' button in the email. This is a unique link that directly takes you to the event. Your attendee profile details are pre-filled.
Option 2 - Go to the Event Page. Click on 'I have a ticket' and log in using the same email.