I have not been able to sleep, what should I do to fix my insomnia?

Sleep hygeine. The most important thing is to maintain a scheduled time for going to bed, get enough exercise during the day, maintain a healthy diet, and not use alcohol or other drugs. If you are still unable to get sleep, there are many over the counter or prescription medications that may help. Most over the counter sleep aids contain Diphenhydramine (benadryl).
Melatonin. Take 2-3 mg of melatonin over the counter is a reasonable and affective sleep aid. If not affective, see family physician. Most over the counter sleeping aids are just benadryl (diphenhydramine). Melatonin is a better choice.