Attach a plow saddle to the horse. Draft horses were traditionally used, but are not a necessity. Ensure the saddle is secure and comfortable on the horse.
Attach the plow to the saddle. Do this in the field to avoid inadvertently plowing ground that you do not want plowed.
Put the reins around your neck after you have the horse started. Use the plow handles to guide the plow. Keep the plow in a roughly straight line, and parallel to the previous line -- or to the edge of the field, if it is the first line.