Where it fits in your routine
Begin with the acne problem you are trying to address. Benzoyl peroxide belongs in acne care, not as a routine extra for everyone who wants smoother-looking skin.
Check whether your product is a wash or a leave-on treatment. Rinse a wash as directed; do not borrow its contact time for a different gel or cream.
If it is part of a prescribed combination, follow that plan and ask your pharmacist about any conflicting package instructions.