Any follower of Jesus who is going to be faithful in the task of bearing witness to Jesus needs to receive God's enabling power.
In the Acts passage, 'power' translates the Greek word dunamis- from which we get words like dynamite and dynamo.
This dynamic power, Jesus tells us, comes through the Holy Spirit at work.
And so, it is here that we discover good news, for the same Spirit who enabled Jesus to fulfill his mission can enable the Church to fulfill her mission too.
Jesus wants us to be filled with the Holy Spirit so that we can join him in that mission, to be his witnesses to the ends of the earth (Acts 1:4-8), and to build the kingdom of God while we are present on the earth.