# thrones were set in place

"someone set thrones in their places" 

# the Ancient of Days

"the One Who Has Lived Forever" or "the One Who Has Always Lived"

# took his seat ... His clothing ... the hair of his head

This passage describes God as sitting down, with clothing and hair like a person. This does not mean that God really is like this, but it is how Daniel saw God in a vision.

# took his seat

"sat down on his throne" 

# His clothing was as white as snow

"His clothing was very white"

# the hair of his head was like pure wool

Possible meanings are that 1) it was very white or 2) it was thick and curly. 

# pure wool

"clean wool" or "wool that is washed"

# its wheels

It is unclear why God's throne is described as having wheels. Thrones normally do not have wheels, but the text clearly states that this throne has some kind of wheels. Use a general term for "wheels" if possible.