The angle should be pretty much level with the ground. The angle of the bar doesn't determine oversteer or understeer, it's the length & placement of endlinks. Shorter the end links means more oversteer which front wheel drive cars are in desperate need of. Longer endlinks mean more understeer which defeats the purpose of an upgraded rear sway. Shortening the endlinks & using the holes closest to the bar will increase the most oversteer.
Angle with car on ground
Here are the instructions which are terrible quality so I had to adjust them accordingly.
