The barends can be placed at any angle on the handlebar. However most riders prefer one of 3 positions. Riders that want an upright seating position normally prefer the barends up. Racers normally prefer the barends down so they can get into a tuck. Others prefer a neutral angle allowing for a seating position between a tuck and sitting upright.
#1 Loosen the 5mm bolt at the bottom of the bar end.
#2 Riders that prefer an upright seated position should try to turn the barends upward.
#3 Riders that prefer a racing tuck seated position should try to turn the barends down.