I believe they are accessed through the trunk by removing the trunk panel on the side of the bulb that needs replacement. the front ones are accessed by removing the front wheel, pulling the plastic inner wheel well lose to access the light.
There is a thread somewhere about how to change them. There is a diagram on all the front end items you have to remove or loosen to get to them. Do a Google search on replacing malibu headlights and add the year. You will find everything you need.