Tip: If you've created a lot of custom questions for your attendees to answer at registration, it's a good idea to extend the registration time limit beyond the default 15 minutes. See below to learn how to do that. 

To get started, from your event's Manage page, select Customize Order Form from the features menu on the left side of the page. (To get to the Manage page, click on My Events at the top of the screen, then click on the name of your event.)

On the Customize Order Form screen, scroll down to the Optional Settings section. You can edit the Registration time limit as you'd like.

When attendees register for your event, they will see a time limit countdown clock on the registration page. When that time limit expires, the tickets they put on hold when they initiated the order will be released and they will need to start the order process from the beginning.