# I have raised up one

"I have appointed one" 

# from the sun's rising

"from the east" 

# him who calls on my name

Possible meanings are 1) that this person invokes Yahweh for his success or 2) that this person worships Yahweh.

# he will trample the rulers

"he will conquer the rulers"

# like a potter who is treading on the clay

Yahweh compares the way in which this person will trample the other rulers with the way that a potter tramples on clay to mix it with water.