They are very easy, although you may have to loosen your front bumper.
Open your bonnet, and remove all the black plug-like things along the top.
Get on your back and unbolt the two bolts holding the base of your bumper in place, one on the left and one on the right.
Unscrew the screw on either side at the front in the wheel arch.
Your bumper should be loose if you give it a little wiggle. No need to remove it completely, but if you pull it so the front lip is resting against the floor, you should be able to access the bolts that are holding the current grille in place. Remove these.
Using common sense, unbolt and remove the current grille.
Put the new grille in place, but notice it doesn't have bolts at the bottom, but instead a curled lip at the bottom which should slide onto your bumper.
Put it all back together again. Job done 8-|
Some steps might be slightly different for your car, but those are the basic steps.