Assuming its the post front bumper - once you have the 2 screws out look along the bottom of the grille. You should see its clipped in. Starting at one side just slowly prise it out by moving grille and area of bumper about till you get it free. Once one side is free it should be easy from there.
Another suggestion would be to undo the screw either side of grille that goes through the 2 upright parts of bumper holding it to the car if you get me as once they are undone it is looser around the grille area and should come out very easy.