All the candles are found on the down different paths of the river:
(1) Follow the first branch to the right. There you can find a candle inside a wooden tree hut. There is also a treasure behind it. Go ahead and take the river back down to the elevator.
(2) This time take the left branch. You will then come to another branch. 2 candles are found down the right branch, the other one is found down the right.
(a) Down the right branch you will have to stop at a building and shoot out a window, pull a lever and grab the candle. Now follow the river back to the elevator.
(b) Down the left branch you will have to stop rather quickly and you will see another hut. The candle is inside, but beware of the spiders that fall down when you grab it.
1. Keep going after you grab the candle where the spiders are. Again be ready to stop quickly or you will float past the ledge you must exit at. After you get out of the raft, you will find a path that leads you to a larger building that contains machinery. The candle is inside after you solve an easy jumping puzzle to cross the gap.
Hope that helped.