Putting on eyeliner was very hard for me to learn as well. As awful as this sounds, practice does make perfect. However, buying a round tip eyeliner pencil is much easier, especially the ones with erasers on the end. They never need to be sharpened, and, more importantly, they are SO much easier to put on. You can find them anywhere where makeup is sold, like Target, Walmart, Walgreens, etc. Now, when you go to put it on, pretend like you're sketching. Don't draw one line without lifting the pencil. That is very hard to get right. Also, don't put it on heavy at first, in case you make a mistake. Just concentrate on following your lashline. As you sketch, if you are drawing on the right spot, go over it a few more times, making it as dark as you want. The key is to do it in small parts, because this will lessen your chances of making a mistake. When you are completely done with the first eye, take a step back from the mirror (which I'm assuming you're using) and carefully study it. Concentrate and try to line your other eye in the same manner. After you are completely done, once again, take a step back from the mirror and make sure both eyes look the same. If they don't, try to match them, and use the eraser on the pencil for help. If you messed them up really bad, and cannot get them to look identical, the only option you really have is to wash it off and start again.
If my advice doesn't help, see if your mom, aunt, or a friend will help you apply it. Just make sure that they are good at it. =) Hope that helps, and good luck!