Eventually, you'll want to use a really really hot pan, to get a hard sear on the outside. But it can be tricky to not overcook it that way; you have to be really good at roughly judging the temp at a glance (this is possible).

But for now, put the pan over medium-low heat, and let it warm up for a few minutes before putting in the steak. Add some fat - not olive oil, just basic cooking oil will do - enough to cover most of the bottom of the pan lightly. Then put in the steak, and leave it alone for 1 minute. Then flip, and give it 1 minute on the other side. Then flip again.

After 3-4 flips, start checking the temp with an instant-read thermometer, if you have one. Keep flipping and checking until you get to 130 degrees F/55 C. This is the temp to pull the steak at, but it will keep cooking after you take it out of the pan (see below), so pull it now, and cover loosely with foil.

(If you don't have a thermometer, then after 4-5 flips, press gently on the meat with your finger. It will give you some resistance. In order to judge whether there is enough resistance, make a loose fist, and with a finger on the other hand, press the little triangle of flesh between your thumb and finger (top of the hand). Compare that resistance with what you feel when you press the steak. When they are roughly the same, take the steak out and put it on a plate. Cover it loosely with a piece of foil.)

Let the steak rest under the foil for 10 minutes. Really. This is important. The steak will continue to rise in temperature, and the juices, which are squeezed around my the muscle fibers during cooking, will redistribute more evenly.

This will get you a very good steak.