Sleeping difficulties, whether they be insomnia, narcolepsy, sleepwalking, etc., are usually caused by either stress or poor sleep hygiene.
If you're having difficulty sleeping because of stress, here's a simple solution:
Sit down with a pen and paper. Don't use pencils, markers or highlighters. Just sit there with your pen. When you start thinking about something, stop and write down what you're thinking about on the page. Keep writing, even if you're thinking negative thoughts. It's OK to think bad thoughts, but don't allow them to control you.
After you've finished writing for a while, read over your thoughts, taking note of things you wrote down that are bothering you. This will show you the thoughts that are keeping you up at night.
Once you've identified them, look up any articles that pertain to them. Read the articles, and write down the thoughts that came up for you as you read them. Don't stop once you finish reading - write the remaining thoughts that came to mind. After you've written down everything that comes to your mind, read the article again and see if there are any additional points that stuck with you.
Continue writing until you've finished reading the entire article. You're probably going to find that some of the issues you were originally thinking of are no longer relevant. Once you've done this, set your alarm for 5-10 minutes before you usually go to sleep.
That's it. You'll never struggle with insomnia again.