The museum's website will announce a release date for tickets 2 months in advance. Example, today they relesaed tickets for July. At the beginning of May they will release tickets for August. You have to be online at 9am on the release day to request tickets. Tickets go fast for weekends.
There are also a limited number of same-day tickets, released online at 6 AM. And you can get walk up passes onsite after 1 pm if available that day.
You have to go to the website.
As far as I know, you get tickets online. They go fast. I got my tickets 3 months in advance.
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