They bow out. At the outer end you will see a opening. Insert a long screwdriver through the hole, pick up the tab of the grill, move the handle of the screwdriver towards the outside of the car. That will bend the grills tab out from the bumper and you can pull the grill loose.
There are two tabs on the inside of the grill which insert into slots in the bumpers central divider, but I find those are harder to work than the one on the outside.