Take your finished oil pastel painting and lay it flat on a paper-covered table in a well ventilated room. The paper on the table will collect any excess fixative and can be rolled up and thrown away when finished.
Shake the oil pastel spray fixative can for a few seconds. Hold the nozzle around 12 inches from the artwork and spray from side to side in a smooth, sweeping motion to give even coverage across the picture.
Once the painting has been covered in one even layer of fixative, let it dry for around 20 minutes. If the painting has many thick layers, it may be necessary to spray another layer of fixative in the same manner after the first has dried completely.
Frame the artwork for display or store in between wax sheets to prevent smudging. Keep your painting out of direct sunlight and in a cool, dry space.