How do you meditate successfully?

I’m very crazy inside my brain. I’m manic and compulsive and obsessive and worrisome and scatter-brained and way over cognitive and not at all peaceful. I have trouble shutting off my brain at night and it takes me around 2 hours to fall asleep. I think meditating would help me a great deal, but I’ve never been very good at it. I had an instructor who told me to focus on one thing (like my son’s face or something). And she said that take that idea and visualize it as a boat going down a river, and try to keep that boat from bumping into the river banks. Well, that just made me even more nuts. Why can’t I steer that damned boat!?