Position the boutonniere on the left lapel of the jacket, tilting the flower side upward and the stem side downward. Hold the boutonniere in place with one hand.
Lift the lapel away from the jacket, and use your free hand to stick the pin through the back of the lapel and the boutonniere stem. The pin should be angled away from the body.
When the pin is pushed through the stem, angle the pin down, and carefully push it through the lapel. This action should resemble sewing a stitch, and it helps hold the boutonniere in place.