Hammies are hamstrings and hamstrings are the long muscles in the back of your thigh, also known as leg biceps, which are really biceps femoris. So, there you go, hammies are biceps femoris.
Now that we've gotten that straight, the stretch is simple. Stand with your feet wider than shoulder width apart and turn your upper body to one side. Now, keeping your back softly straight, bend out over the leg you are facing and touch the ground. After you've gotten somewhat comfortable there, fold your arms behind your back, resting them on your butt, and push your chest forward while raising your head and straightening your back into a bit of an arch. To deepen it further, you can now lower your head towards your knee and soften the arch in your back.
Repeat on the other side. Don't forget to breathe! Always!
Still more stretches to come.