1. Open the passenger side door. Remove the end cover located on the side of the instrument panel in the top right corner. Remove the screw affixed to the side of the glove box.
2. Open the glove box door and remove the attached screws from around the glove box.
3. Lower the loosened glove box housing.
4. Unplug both wire cables and remove the glove box.
5. Pull the three tabs to release and open the filter door.
It is not as simple as this implies. You end up taking half the dash apart. I think they did this for sound proofing. I won't buy another one like this that requires this type of invasiveness to change a Fu...ing filter.
Cabin air filter is located under the glove compartment.
Open the glove compartment. Here unhook the damper cord from the right side of the glove box compartment. With attention pull the plastic hook out and then introduce it back through the small hole from the glove compartment. Read more here http://filterlocation.com/change-2010-2011-buick-lacrosse-cabin-filter/