See Part 1 of learning to use Om in your meditation by clicking Here. In this video, BDivine takes you through an actual Om meditation. She does 2 chants, then a pause to allow you to visualize what it is you would like to heal. Then another set of 3 Om chants. This is followed for a series of 7 and then she ends it. If you feel a little bit of a tingle on your face or in your ears, know that that is part of the effect of the Om and is perfectly normal.
Try to do this chant once per day and within a month to three months, what you are focusing on should manifest. Let us know how you do with this meditation!