At the beginning of the game, pick up the snack box from the floor. A couple of snacks will fall out and a rat will come out to go eat one of them. Pick up the rat and after a bit it will bite you. Repeat this several times and you will eventually die.
Here's a video walkthrough. This achievement unlocks at around 4:00.
If this is your first death, you will get REDSHIRT as well.