There are a number of fixing bolts to remove and the under tray is the first to do..the under tray is held on by 13mm bolts and it needs to be either dropped at the front end or removed completely..your car will need to be jacked up to gain access to the bolts..

This is the under tray..






The bumpers on the stilo differ in style but are removed in exactly the same way..





This is the 5dr



The fixing points on both are the same and all will need to be removed before the bumpers can be taken off..lift the bonnet and just above the grill you have 4xtorx bolts shown Fig 1 these are T30 torx.. you also have side fixings on both sides holding the front wings to bumper .. to get at those you will either have to remove the inner wheel arch liner or remove enough screws to push it back out of the way to give you access to the bolts connecting the wing to bumper..

This is the arch liner being removed



This is an arch liner after removal..



Also shown on the bumper photo are the fixings under the bumper there are 4 of those to remove as well .. once those are out the bumper should lift off..make sure you use another person here to avoid damage to the paintwork on your car.. refitting is a reversal of taking off once again I advise an extra pair of hands to help you get the bumper back in place ..