Cow pose is usually performed as a flow or “vinyasa” with Cat pose, below. They are great poses to start with to warm up the body.
Begin on your and knees, with your hands directly below your shoulders and your knees hip-width apart. As you inhale, round your back as much as you can. Tighten the abdominals, and imagine that there is a rope around your belly, pulling it up towards the ceiling.