This is an excellent asana to prepare the legs for padmasana. It is also a good meditative asana in its own right.
Sit on the floor with the legs extended in front of the body. Fold the left leg and place the left foot on the floor beside the right thigh. Then fold the right foot on top of the left thigh. Without straining, try to place the heel of the right leg as near as possible to the abdomen. Adjust your body to a comfortable position. Hold the back, neck and head upright. Place the hands on the knees or clasp them and place them in the lap. Close your eyes and relax the body.
Preparation for padmasana
If you can do ardha padmasana then you are well on the way to mastering padmasana. Use this asana to prepare the legs for padmasana. In this respect alternately fold one leg on top of the other, if necessary, while doing pranayama or meditational practices. That is, first fold the legs so that the right leg is on top. When this position becomes uncomfortable or the next time you sit for practice, place the left leg on top. In this way you will loosen up both legs. If one of your legs is more flexible than the other, then you should spend more time sitting in ardha padmasana with the least flexible leg on top. This will increase the flexibility of the leg.