This is an eternal favorite user interaction question.
Luckily, it has an easy solution and it's documented in at least 2-3 places. (Not saying that makes up for the kludgy design...)Tap the menu button.
After the bottom bar slides up again, tap on any of the tabs.
(If you don't do that, they'll eventually slide out again.)
If someone sees a better way to do this, I'll implement it...