Getting in this pose can happen from several different postures: From Down Dog, Table Top or Lotus the object of this pose is to bring one knee forward to the side edge of your mat with the other extended behind you. Lengthen through the quadriceps, the front surface of the back leg and abducted the front leg knee bent with the heal of your front foot under the hip crease of the opposite side. Melissa has demonstrated this with a variation adding a twist and moving the heal away from the hips.
Some effects of eka pada raja kapotasana:
rejuvenates the spine, exercises the neck and shoulders, the thyroids, parathyroids and adrenals receive a rich supply of blood, enlivens the gallbladder meridian and increases vitality.
When practicing this move breathe through each movement to get there, play with your own variation while having compassion for your body and do only what feels good, I personally love a forward fold here releasing everything to the Earth giving a piriformis and sciatic nerve stretch.