There are a couple of techniques I have heard of, one is the Rope Technique and another is Robert Monroe's Technique. You can google them for more info and I also have provided links below to a couple of sites that explain each technique step by step :)
my first question is are you able to use your third eye? What i mean by that is have you meditated before? Meditation is to help you align the chakras and put you in a relaxed state. Once you are within that state, you will be free to astral project(remember to protect yourself in both forms).