Ask yourself when is it that you feel like cutting. Most people cut as a coping skill, but it is not a healthy one. Develop a list of about 10 coping skills you could do instead. Some could be distractions like writing your thoughts out, doing a clean up task, calling a friend. Others could be ways to relax like taking a walk, taking a hot shower, or listening to relaxing music.
In addition, remove everything that you cut with from your room or bathroom or wherever it is that you cut. If that urge is overwhelming try snapping a rubber band on yourself or holding cold ice on yourself. You will feel a physical pain, but not a life threatening one. Talk to your friends. You need some good peer pressure. Have your friends who do not support cutting check in with you. If your parents do not know, tell them. It is a sign of strength when you ask for help. They can help find a counselor for you who will help you set up a safety plan and help you work through issues that might be causing you to want to cut yourself.