Firstly you roll the person over to there side and tilt there head up (so if they vomit or coff up any fluid they wont choke or swallow it).gentaly shake them to see if they react, talk to them and...
Its the area between the ribs, just below the sternum (chest bone) that is used as a reference point for the best location for CPR (cardio pulminary resusicitation) compressions.
During CPR, you want to make sure that the xiphoid process is not compressed at all as it may break or dislodge and damage the liver. The compressions should be in the middle of the sternum well...