The psalmist opens with a description of the nations in opposition to The LORD and His King. This is given in the form of a question why they are in such attitude. He then proceeds to declare the Lord's contempt for them, and in verse 6 The LORD is the Speaker, announcing that, notwithstanding all their opposition, He has appointed His King. The next section (7~9) gives us the words of the anointed King, who declares the decree of His Kingship.
The Son of God is to receive dominion from His Father and exercise it to subjugate all these opposing forces. The order of procedure is indicated, "inheritance," "possession," "administration." The psalm ends with an appeal to the kings and judges to show their wisdom by submitting themselves to The LORD's King.