# walked in all the ways of Jeroboam son of Nebat

"did all the same things that Jeroboam son of Nebat did" 

# in his sins by which he led Israel to sin

"his" and "he" refer to 1) Baasha or 2) Jeroboam.

# in his sins

"he sinned as Jeroboam sinned"

# to provoke Yahweh ... to be angry with their worthless idols

"to make Yahweh, the God of Israel, angry because they worshiped worthless idols" 

# their worthless idols

"their idols, which are worthless"  

# the God of Israel

"Israel" refers to all of the twelve tribes descended from Jacob.