i did it in the following way on the c200 which should be similar to youe emblem.
i used dental floss believe it or not!
take a 12 in long piece of dental floss and prise it behind the the back surface of the the star,pull the the two ends of the floss together as the floss is pulled towards the middle ot the star,then hold the two ends of the floss and pull them at right angles to the star-i hope this is clear-on no account use a screw driver as this will ruin the paintwork and may break the star.
the push in prongs of the star are located in the middle near where the three arms of the star meet.
also when refitting make sure the arrow at the back of the star is pointing in the correct direction, as otherwise the star will not sit flush with the trunk of your car.
hope this helps!