If you want a simple eye drawing to copy step by step, take a look at this drawing an eye step by step.
The Anatomy of the EyeWhen you learn to draw eyes, it is useful to think about the anatomy of the eye. Watch a friend's eyes as they look from side to side. You can see that the eyeball is not a perfect sphere. The cornea bulges out in front of the iris (the colored part), so that the while the iris looks flat, reflections from the front of the eye show a curved surface. When drawing, this detail is important, because when the eye changes position in the socket, it makes the shape of the eyelid change slightly.
How you draw the eye also depends on the angle of your subject's head. If they are are at an angle or three-quarter view and not looking directly at you, the eyes will also be at an angle - so you are looking at them in perspective. Because the pupil sits in the plane of the iris, and being in perspective is oval rather than circular. Do you have a coffee cup or even a round bangle or ring handy? Hold it at an angle and notice how the circle changes into an oval as you turn it, to see how the appearance of the eye changes.