Insomnia can be caused by several different things such as poor sleep habits, depression, anxiety, lack of exercise, chronic illness, or certain medications.
There's really no cure for Insomnia and it's usually a lifelong thing that someone suffers from and the only real way of getting to sleep when you have Insomnia is to take some sleep medications to help you drift off to sleep.
Being stressed out and worried about things can also stop you from sleeping and cause Insomnia so avoiding stress and worry can sometimes help with Insomnia.
Taking some Apple Cider Vinegar before bed can sometimes help people drift off to sleep when they're suffering from Insomnia.