How do i change low beem head light - 2004 Porsche Cayenne

Go to Autozone, they will do it for free at most stores.

Otherwise, the method is pretty straight foreward. You will have to remove a small plastic access pannel over the headlight.
Under there, in a space designed for a small child's hand, you will see a black collar at the base of the wires running into the headlight. You need to rotate that counter clockwise about a third of a turn, and slide it back along the wires. Pull gently on the connector those wires go to, and do not pull it by the wires themselves. there is an O-ring holding the bulb in the housing. Once you have it out of the housing, there is a small catch that is pretty obvious. You will need to pry that catch up slightly to get the bulb out of the socket on the end of the wires. Reverse the steps to reinstall the bulb. Never touch the glass part of the bulb. The oil from your fingers will create a hot spot on the bulb when it is on, and cause it to crack in a matter of days.