While meeting with them, he enjoined them not to depart from Jerusalem, but to wait for "the promise of the Father 3 about which you have heard me speak;for John baptized with water, but in a few days you will be baptized with the holy Spirit.But you will receive power when the holy Spirit comes upon you, and you will be my witnesses in Jerusalem, throughout Judea and Samaria, and to the ends of the earth."The 9 days between Ascension Thursday and Pentecost is traditionally set aside for a novena to the Holy Spirit, asking for His gifts to be poured out on us. As the Church uses these days, we can join with our brothers and sisters and pray together, like the first Apostles in the upper room, for the Holy Spirit to come upon us and give us the courage to do what God will have us do in this life.
When he had said this, as they were looking on, he was lifted up, and a cloud took him from their sight.
When they entered the city they went to the upper room where they were staying, Peter and John and James and Andrew, Philip and Thomas, Bartholomew and Matthew, James son of Alphaeus, Simon the Zealot, and Judas son of James. All these devoted themselves with one accord to prayer, together with some women, and Mary the mother of Jesus, and his brothers.
And suddenly there came from the sky a noise like a strong driving wind, 2 and it filled the entire house in which they were. Then there appeared to them tongues as of fire, 3 which parted and came to rest on each one of them.
And they were all filled with the holy Spirit
~Acts 1: 4-5, 8-9, 13-14, 2: 2-4
The novena is here on EWTN's website.