As He ascended into heaven, our Lord Jesus Christ promised that the apostles would receive power when the Holy Spirit would come upon them. The disciples wanted Jesus to restore the earthly kingdom of Israel. They could not conceive of power in any sense other than military might. Jesus, having all power in heaven and earth at His disposal, sees things differently. The power He will give will be used for conversion, not revenge.
The Greek word dynamos translates literally as power or capability. It can also imply influence or authority. Think of some of the other English words that come from this Greek root: dynamic, dynamite, dynasty. Power, for Christ, implies not the assertion of your will over others (the philosophy of "might makes right"), but the ability to move hearts, to win souls for Christ our King, and to change the world through the mighty deeds of God's grace. Any physical prowess we have is put at the service of the spread of the Gospel. Look at what the apostles did with this power: they did not drive out the occupying Roman army, but instead brought many of them to faith in Jesus and baptized them!
The Ascension of our Lord Jesus ultimately reminds us that our goal is not here on Earth. We long for heaven--to be with Jesus in His Kingdom. So the power we have in this life must be directed toward that goal. "Thy Kingdom come, Thy Will be done" on earth by the power of the Holy Spirit, so that we might draw all souls into union with Jesus Christ in heaven.