There are several things you can use to spray fix drawings with sheddable media like charcoal or chalk pastels.
Workable fixative is a poor fixative because it keeps the drawing workable, meaning you can still erase and change the drawing.
This is a superior fixative and should only be used once the drawing is complete.
Aerosol hairspray is a cheaper less toxic alternative to fixative. It may cause a small amount of wrinkling of the paper and it may not be archival, but it's great for students.
STOP! READ the back of whatever product you bought completely.
Only use spray fix in well ventilated areas away from people, pets and plants that you eat.
Spray a light mist from about 6-10 inches from the surface of the paper.
Sweep back and forth systematically to cover the whole sheet evenly and lightly.
Many light coats are superior to over wetting the paper.
When you are done fixing your drawing, allow it to off gas in a well ventilated area for several hours. Leave the drawing open to air out until NO ODORS are present.