Just transfer some BAT from your wallet or exchange to the address you will find in your Brave browser settings. At this point it only works for the pc/laptop browser, not in the mobile versions.
I have changed to Brave on my mobile, pc and laptop and the browser performs very good. It will be interesting to see once they start with the functionality that pays BAT to users for browsing, as I understand this will be in the first quarter 2018.
Yes, I am very interested to see how BAT integration works.
Some see the browser requirement as a hurdle for real adoption. I see it as a great marketing vehicle! So far, I only heard good things about the browser.