First of all draw a circle.
Now draw this lines it'll help you to locate the area to draw eyes and mouth.
Now start Drawing Madara's Face beneath the circle.
Now draw His hairs hanging down the side of the face. Just like you can see in the picture above.
Now draw Madara's eye and rinnegan in it.
Now draw Madara's mouth at the end of circle by drawing a curved line.
Now draw his clothes and Armour as you can see in the picture above.