Simply use the "puff" bottle to apply a thin dusting over the skin around your stoma. Allow excess to fall off and proceed with applying your ostomy appliance. Stoma powder is meant to absorb moisture and to help protect peristomal skin.
Stoma powder is composed either of karaya or pectin and create a barrier for weeping peristomal skin. Do not substitute baby powder for ostomy powder which is either composed of pectin or karaya. Baby powder can interfere with the adhesion of your ostomy appliance and does not absorb moisture around the stoma as well as stoma powder.
Other ways to apply involve skin barrier wipes/sprays to make the powder wet and "crust" before applying the ostomy appliance.