depending on your hand size and which version you have...

wrap your index on the outside of the brake lever and wrap your middle and ring finger on the hood body.

going to higher gear↑: Flick your wrist to access the thumb shifter.
going to lower gear↓: Use your middle and ring finger on the paddle shifter while braking with your index.
-or-
Swoop down in gear(s) first, then apply brakes with as many fingers as you want.

why do you need to use the brakes when going up in gear anyways?