This trophy is simple enough, since there are multiple occasions where you will find yourself using melee combat, and for nearly all of Chapter 2, it's your only option. If you fail during that section at all, you may even earn this before you even finish that chapter. If not, it will come naturally shortly thereafter. Note that any type of melee kill counts for this trophy, including stealth kills.

As with all of these trophies, you can restart a checkpoint to farm it if you want to get it out of the way early.