You can use a picture of your own eye or one from the internet. If you’re having difficulty drawing the eye shape, look at drawing books and do a lot of practicing. With time, you’ll be able to draw it.
Do not draw the eyelashes yet, this will be done later.
Having a white pencil will help you blend over areas if you make a mistake. Don’t sharpen the pencils too much, as the tip is more likely to break if it is at a very sharp point. When you’re starting, it’s usually a good idea to have a color wheel with the different tones and colors so you can mix and match them until you get to the desired colors for the eye.
Different hues of each color will give you different combinations and hues. Not every orange is made equal, for example. Try out different mixes until you get the desired color.