It is very simple, don't overthink it. Go to a quiet place with no distractions, let go of everything mentally and physically, be totally relaxed, don't think of anything (i.e. Pratyahara) but just try to focus on a point within the blackness (i.e. Dharana) and hold your attention there (i.e. Dhyana) when you feel a distinct bodily sensation.

Try and do this before falling asleep in your bed at night and your quality of sleep will improve greatly. You can also do this just after you wake up in the morning in your bed (but before looking at your phone, talking to your spouse etc.) and you will feel more refreshed than normal.

Once you get the trick you can actually use a home blood pressure monitor and see the changes in physiological parameters yourself.