# will appear to them

"will be seen in the sky by his people" or "will come to his people"

# his arrows will shoot out like lightning!

The Israelites sometimes thought of lightning bolts as arrows that God shot. 

# blow the ram's horn

People blew into rams' horns to give signals in battle and on other occasions. Here the ram's horn is blown as a military signal.

# will advance with the storms from Teman

"will march from Teman with the storm winds"