Do you just walking in or do you have to have a ticket to enter?

If you are feeling lucky you can turn up @1.00pm and get in line without a ticket and you may get in. Or go online at 6.30 am on the day you are in DC and book a ticket for the available time slots you either print the timed ticket or show the ticket from your smart phone when you show on time to the museum entrance.. It's easy and it's free

You can get tickets online at 06.30

Need a ticket in advance or come early to get same day ticket.

Ticket... which you get online