If your sitting around waiting for Jesus to sit on David's throne then you've compoetely missed the boat.
(Act 2:29) Men and brethren, let me freely speak unto you of the patriarch David, that he is both dead and buried, and his sepulchre is with us unto this day.
(Act 2:30) Therefore being a prophet, and knowing that God had sworn with an oath to him, that of the fruit of his loins, according to the flesh, he would raise up Christ to sit on his throne;
(Act 2:31) He seeing this before spake of the resurrection of Christ, that his soul was not left in hell, neither his flesh did see corruption.
When did Christ sit on David's throne? I know you have reading comprehension problems so I'm gonna walk you through it. David, being a prophet, said that God would RAISE UP CHRIST (resurrection from the dead), TO SIT ON DAVID"S THRONE.
Get it? When Christ was raised from the dead, that's when he sat on David's throne, permanently, forever.