Hm that's a hard question. Your brain is noisy? You can't relax? Is this what you mean? Talking to ourselves is pretty common but if it is causing you not to sleep or fall asleep, good question as to how to quiet it. Can you try visualization or meditation?
There are a lot of meditation music on computer that you can focus, and can be soothing and relaxing and also some of the music for helping you to get to sleep.
Another thing to try is write down what you're thinking, get it out of your system, and then go to bed. You never know, you might find a writer inside of you.