You would never give the keys to your house to a stranger you knew nothing about. Keys are given to people in trust, only after they have proven that they will be responsible. God does it backwards. He gives us the keys first, then He develops trust in us.
We must live in close communion with God to even think about using our authority. When the sons of Sceva tried to cast out an evil spirit by the Jesus whom Paul preaches…the evil spirit answered and said, Jesus I know, and Paul I know, but who are you? (Acts 19:13-14) It did not go well for the sons of Sceva. They tried to use authority without having a relationship with Jesus first.
Get to know God. Victory over the enemy comes from knowing how good God is. Get to know His goodness and you can speak to the powers of evil with greater understanding. Using your authority will come from the revelations you get from your devotional time. Listen to the voice of God and He will teach you how to use His keys.
You are meant to be a world changer. You are meant to bless the lives of others. Coming into agreement with what God wants to do through you will take you to a new level of spiritual maturity.