From Tadasana, step to face the side of your mat with feet 3.5-4.5 feet apart or as wide as your arms can reach (wrists above ankles). Then turn your right foot to point parallel with your mat and your left foot can slightly angle towards the right foot. This stance is similar to Warrior 2 pose.
Now bend your right knee until your thigh is parallel to the floor and your knee is directly over your ankle. Place your right hand down flat on the floor if you can, or use a block for more support. The work in this posture is to rotate your spine up towards the ceiling, while keeping your back foot grounded to the outer edge with arch of the foot lifted. It is helpful to think of this rotation from your core. The strength developed will help support a healthy lower back and strong legs and hips.