To stretch, lengthen and relax the muscles of the inner thigh (the adductors or Vastus group of muscles) in order to increase mobility of the hip. Also to stretch the inner ligaments of the hips and pelvis / groin region.
Sit on the floor with your hips and knees flexed. Place your feet close together.
Slowly and in a controlled manner allow your knees to fall outwards until the muscle tension prevents them from falling further. You can either hold your feet together or use your hands (or elbows) to exert a gentle pressure on the legs (by pushing the knees outwards). Hold for 20-30 seconds, relax and repeat the prescribed number of times.
Try to flex your knees and hips as much as comfortably possible (by opposing your feet and heels together) to make the stretch more effective. Keep your back straight. Increase the stretch by gently pushing your knees further outwards and downwards.