Jesus was taken up after He gave orders to the apostles. He presented Himself alive by many convincing proofs appearing to them over a period of 40 days and speaking about the kingdom of God. He told them stay in Jerusalem to be baptized by the Holy Spirit (Acts 1:1-5). Holy Spirit power begins when Jesus is alive in your heart and you hear His word.
Jesus said they couldn't know when He would be restoring the kingdom to Israel. They would receive power when the Holy Spirit came up them and be witnesses in both Jerusalem, Judea and Samaria, even to the remotest part of the earth. Jesus was lifted up and a cloud received Him out of their sight. Two men in white clothing said Jesus would come in the same way as they watched Him go into heaven (Acts 1:6-11). Holy Spirit power equips you to be witnesses of Jesus to people everywhere.
The apostles returned to Jerusalem, entered the upper room and with one mind continually devoted themselves to prayer along with the women, Jesus' mother, Mary, and His brothers (Acts 1:12-14). Holy Spirit power stays fresh as you continually devote yourself to prayer with others.
Peter said to the 120 people present that according to Psalm 109:8, another person should take over Judas' office as apostle. They would choose one man, a witness who accompanied them from the baptism of John until His resurrection. They selected two men and after prayer, they drew lots and Matthias was numbered with the 11 apostles (Acts 1:15-26). Holy Spirit power to make leadership decisions comes by selecting appropriate sections of Scripture and prayer.
Is Jesus alive in your heart? Are you listening to His word found in the Scriptures? Are you praying with others to stay fresh as a witness of Christ? Are checking out Scripture and praying for any major decisions?