using haarcascade in bbb

ive installed opencv in bbb and found the location of haarcascade dace detector at
/usr/share/OpenCV/haarcascades/
how do i specify the path to get access the classifier
i tried root:/usr/share/haarcascades/<> and got error
what additional detail should i add while using haarcascades

May be this will help

http://coherentmusings.wordpress.com/2012/06/24/getting-started-with-opencv-on-beagleboard-xm/

the face detection part is not working using haar classfier even with the code provided in the link
anything to configure or any prerequisites for using haar cascade method?