The figure-4 stretch is a commonly used hip stretch that targets the internal rotators of the hip. This includes the gluteus medius and minimis, quadratus femoris, obturator externus, and at 90 degrees of hip flexion (as in the stretch position), the piriformis and some of the gluteus maximus.
To know whether you would benefit from this stretch or not, you should know whether you have adequate external rotation of the hip. You should be able to get about 40 degrees of external rotation. In a seated position, with your hands on your hips, rotate the foot upwards. You should be able to contact the heel above the opposite ankle without hiking the hip.
To perform the figure-4 stretch, lay on your back with one knee bent and bring the foot of the hip you want to stretch to that thigh. You can grab the back of the thigh with both hands to pull the leg in closer and get a deeper stretch.