Event pages are public by default as soon as you create them, but you have option to Archive your event to hide it from public viewing and prevent new registrations.
To archive your event, after logging in scroll down to the event you want to archive and then click "Archive". The event will disappear from your "Active Events" listing and will be moved to a new area called "Archived Events".
On the other hand, if you'd like to un-archive an event and make it public again, from the Admin Dashboard page (the first page you see after logging into LaunchTrack) find and click the "Archived Events" tab, and then click "Unarchive" next to the event that you had previously archived. The event will now appear in the "Active Events" tab.