Where does a rear strut bar go? I have heard it goes in the trunk but where exactly does it go?

 

On top of the strut tower at the top of the wheel well usually. You might have to remove some panels before you find it. Once it's visible it should pretty obvious.

img src="http://www.k-series.com/Images/Tech/EP_REARSTRUT/EPStrutBar.jpg"

Yours might differ from this, it's the same idea

 

I can't link pics!, here