It's very simple! In the beginning we recommend trying it out in a sitting position and slowly easing into it while giving the muscles time to relax.
It is fine if the stretching is slightly painful, it should be. Otherwise you are not progressing.
Make sure you don't overdo the stretching.
When you feel the stretch, stay in that position for about 30 seconds before taking a short break.
Then do the same for 2-3 more rounds before switching to the other leg.