After Jesus’ resurrection he spent time with the apostles and told them that God would send down the Holy Spirit to them just as he had promised.
He sent them out to tell people about him and the Word of God. He led them out to Bethany, outside of the city and blessed them.
He was then taken up in a cloud into Heaven. Two men then appeared clothed in white robes and asked why they were watching the heavens. They said “Jesus has been taken from you into heaven, but someday he will return from heaven in the same way you saw him go!” (Acts1:11)
The ascension shows Jesus returning to his Father and later at Pentecost the Holy Spirit descended on the apostles, just as Jesus had promised.