Jesus made the promise to give us this power and authority in Matthew 16:18 when he said to Peter: "The gates of Hades will not be able to withstand or withhold the advancing church." Jesus was going to build his church. The church was going to advance. The gates of Hades could not withstand it.
Jesus is saying that he who is in us is greater than he who is in the world. His power is greater than the power of the enemy. When there is a head-on conflict between the power of the enemy and the power of God, the power of the enemy will lose every time.
How do we then live and walk in this power and authority? We understand from our last session that the world we live in has two realms—the natural and the spiritual. We need to be able to know how to live in this spiritual realm in a way that affects the natural realm. Instead of the spiritual realm only affecting me, I need to be living in a way that affects the spiritual realm, which in turn affects the natural realm.