This is practice to train awareness of the breath.
The breath is an anchor for much our meditation practices and its from the breath where we can notice everything else that’s going on and it’s to the breath that we return if we get lost.
In this instance the mantra will be attached to the breath to make it easier for you to hold your attention there.
For those already accustomed to meditating on the breath you could try this technique for a month or so and see what you notice.

Tutorial

1.) Choose a mantra you will work with
this could be
*a single word like Om, Lam, Vam, Ram , Ham, Yam (or any word of your choosing that won’t activate too much mental charge when repeated) that you will repeat as you breath in and out
*In (on the inhalation) & Out (on the exhalation)
*counting each breath 1 - 10 then starting again.

2.) Set a timer for the duration of you will meditate for (anywhere between 9 - 30 minutes is great) 3.) Sit with a long, straight spine
4.) Take a moment to tune it with you breath, then silently repeat the mantra with each inhale and exhale.
5.) If you notice you’ve stopped repeating your mantra or have lost awareness of your breath repeat step 4 and continue
6.) When your timer goes off to signify the end of your meditation take a moment to notice how you feel, to reflect on the meditation and to write what you noticed in your journal.