Its very easy.
Above the grilles there's about 4 black screws that mount the bumper to the black trimming where the bonnet locks into.
Unscrew those 4 screws, then gently pull the bumper away a little bit so that you can squeeze your hand down to the back of the grilles. While looking thru the grilles from the front, find the clips then unclip them. Push from behind.
Simple as that.