How should we interpret Old Testament prophecy?

Les explains that the Old Testament must be taken as it unfolds, not with the cart before the horse. He notes that after Christ's rejection and crucifixion, Psalm 110:1 shows the Father inviting the Son to sit at His right hand until His enemies are made His footstool; that was the invitation for the ascension, and He did. But according to the Old Testament, He would not have stayed there long before coming back to set up His kingdom—if. Les says that the if makes it hypothetical, because it was all based on the obedience of the nation of Israel and Israel's belief that Jesus was the Christ. In Acts, Peter and the eleven preached to Israel that the one they crucified was the Christ, their King, alive and able yet to come and be their King. Les says all these things were prophesied to fall right in place to the coming of the King and the kingdom, and then Israel could have evangelized the Gentiles. But Israel rejected it in unbelief, and God instead turned to the Gentiles with the age of grace. So the point is to take it through the Old Testament as it unfolds, not put the cart before the horse.