This is core of the message of Good News. God’s world is real. God is in control. God wants us to be loyal and do what He wants. God has a plan to be implemented. His anointed one, Jesus the Messiah, is King. Jesus is to be obeyed. Jesus is the Master.
So, after His resurrection, he met with the disciples face to face. The had no doubt about the resurrection. They saw him and talked with him for 40 days.
In face-to-face meetings, Jesus talked to them about things concerning the kingdom of God.
(Acts 1:5 The Message)