Psalm 81 gives several instructions for worship. It doesn't come right out and say, "this is how you should worship" but it is all in there.
Sing and shout
"Sing for joy to God our strength; shout aloud to the God of Jacob!" v.1
"Begin the music, strike the timbrel, play the melodious harp and lyre." v.2
Celebrate special feasts
"Sound the ram’s horn at the New Moon, and when the moon is full, on the day of our festival;" v.3
It's a command, not a suggestion
"this is a decree for Israel, an ordinance of the God of Jacob." v.4
Remember what God has done in the past
Don't worship any other gods
"You shall have no foreign god among you; you shall not worship any god other than me." v.9 (8-10)
There is condemnation for those who do not listen to God and reward for those who do.
The choice is yours.
Will you answer God's call to worship Him?
Will you listen to Him?
Will you be satisfied with the blessings He gives?