Real easy, as the description says. You need to reach level 5 in multiplayer. This will come very quickly if you have played an online FPS before, i got this after my third match. Remember that you can make your own loadouts after you reach level 2 to suit your playing style. I found the premade loadouts to be lacking except for the super shotgun. I went with the combat rifle at level 2 (3?) and later with the burst rifle (which is a monster) and got top score in my third round with it.