I am assuming you the belt tensioner. This is mounted at the pasenger side of vehicle at the front of the motor. It is easiest if you remove the air cleaner assembly from the front of the vehicle. If you do not have serpentine belt tools, you will have to use wrenches or a rachet with some length to them to give you leverage to release belt tension. The most important thing is to look at and remember the routing of the belt, there should be a diagram on the radiator support, but if it is not there, it can take a long time to figure out the correct routing by trial and error. You will put your wrench or tool on the bolt head that holds the pulley and you wiil push the that tool in the proper direction to release the tension and slide the serpentine belt off of the pulley, then slowly let the tool go back in to other direction until it hits its' travel stop. The tensioner is now fully released of tension, you can now unbolt the old tensioner(should be two bolts holding it in place) compare your parts side by side. Fi they d not match at all the angles, you may have the wrong part. Wrong angles will make it difficult if not impossible to install or not have proper tension to tighten the belt, so double check everything. Then reinstall in the reverse order. If you don't own a variety of tools, you may want to check with a rental company about the belt tool. Good luck.