Lie on the floor with your entire body from head through to glutes touching the floor. With your feet flat on the floor, lift your knees so that your legs form a 90 degree angle. Put your arms out to stabilize yourself
Raise your hips of the floor until there is a straight line from your shoulders to your knees. Pause at the top and really feel your glutes, hams and core working in harmony.
Ideally if you feel a good connection at the top of the exercise, then the longer you can hold it the better. At first this might just be a second or two, but eventually you should hold for 4 or 5 seconds.