OM Meditation takes the powerful chanting experience of monks use to reach enlightenment and brings it to your practice. For this session sit in a comfortable position with good posture. You are encouraged to join in with the chanting or if you prefer you can breathe In time or just let the sounds wash over you. Personally I prefer to use headphones that are comfortable during this session as it really immerses me and the experience and helps me to not be distracted as i go through.
The video itself is 1-hour long however feel free to use as much of the session as you want to. If that's just 5-10 minutes long then that is fine. This is your practice. Feel free to do it how you want.