Let the breath be the size it is
You do not need a dramatic deep breath. Breathe in gently through your nose or mouth, whichever feels comfortable.
Make the way out a little longer
Let the exhale last slightly longer than the inhale. No holding. If counting helps, try breathing in for three and out for four. If counting annoys you, leave it.
Do it three times
Your attention may wander. Bring it back without quarrelling with yourself. Shallow breathing still counts. Stopping is allowed if you feel uncomfortable.