Walking in consistent freedom will be a long difficult journey. You are going to need help. You need people that can hold you accountable and be there for you. There are many people who have been where you are and have found new life and freedom from addiction. Specifically regarding substance abuse, some people start with a detoxification program for the first days as a safe way to overcome withdrawals. Others have worked through addiction recovery programs at inpatient or outpatient treatment centers to help get them and keep them on the right path.
Whatever addiction you are facing, surround yourself with a healthy, loving community of people who want God’s best for you. Remember: you are not meant to do this alone! Jesus promises in Philippians 1:6 that He will begin the process in you and carry it out in His power.