Take steak out 30 minutes before cooking, you want it to come towards room temparature so that it's relaxed when you cook it as this helps prevent it from being tough. Put your oven on a low heat (around 60c)
If you have a griddle pan (if not a skillet/frying pan) on a high heat and let it get searing hot. Cut a garlic clove in half and rub each side of the steak with it, then salt and pepper, and then a bit of oil. Not too much oil though and the more liquid in the pan the more you will stewing the steak in it's juices rather than searing for a nice texture and flavour.
For medium it's around 3 minutes each side, however the best way to check is by putting your thumb a finger and pressing the part of your palm underneath the thimb. Thumb to little finger is well done, ring finger is medium, middle finger, medium rare, index finger is rare.
When you've cooked it to your preference place it on rack in the oven with a plate underneath to catch the juices, and let it rest for a few minutes. You can deglaze the pan and add the juices from the steak, with a knob of butter and some red wine, to make a sauce.