The Psalmist not only calls attention to the fact the LORD rules over all but there is a literal place where He exists and rules from.
However, it is great to know that God is approachable. At the same time, we can always come to Him through our prayers and we can have a relationship with Him. This connection with God should bring joy to our life as well.
Why should we praise Him? One reason to praise Him is because of His love for us. God wants us to spread that love to others so they can too enjoy a relationship with Him.
 Bless the LORD, ye His angels, that excel in strength, that do His commandments, hearkening unto the voice of His word.
 Bless ye the LORD, all ye His hosts; ye ministers of His, that do His pleasure.
 Bless the LORD, all His works in all places of his dominion: bless the LORD, O my soul.
In these final three verses, David asks others to join in praising God for the appreciation of all that He has done for our lives and our world. David asks angels to join him in verse 20 and he asks the heavenly hosts to join him in this praise fest to God in verse 21.
In verse 21, David asks his “minister” (servants), which I can assume is fellow believers, to join in this praise to God for all the good He has done for and in our lives.
The point of these verses is that the praise of God should not just be something we do alone, but should also be a group effort whenever possible.
Perhaps the use of “angels” and “hosts” in these verses indicate there are different classes of these heavenly beings. Whatever the case, the important idea is that we take time to regularly praise God. If we are going to spend eternity with Him, we might as well get used to the idea of giving Him praise now, as I suspect we are going to be doing a lot of that through out all of eternity.