Accidentally turned on TalkBack, how do I turn it off?

I accidentally turned on TalkBack in the Accessibility menu. When I turned it on, I got some kind of walkthrough on how to use it. I couldn't cancel it. So I turned off my phone. When I turned it back on again, it took me 15 minutes to unlock my phone. Apparently I had to touch a button to give it focus and then double-tap it to click it. Now my question is: how do I turn this off? I can't reach the settings because I don't know how to access a dropdown and I can't scroll through all my apps.