Answer:
Find pictures of horses that look like what you want to draw. Break the horse down into basic shapes first. Draw the leg muscles and joints with circles and ellipses, use circles and rectangles for the face, and make the belly out of a curved cylinder or rectangle shape. Make sure to draw these lightly, and look at a reference picture of a horse to make sure your proportions are correct. Does everything measure up correctly to each other? If it does, then draw darker lines, contouring the actual shape of the horse body along the shapes you have already made. Do this until you have a good horse shape, then clean up the guidelines and shade/color your horse!