Turning over the cauldrons basically gives a step to go onto to reach some slightly higher areas if needed- nothing particularly useful.
You are right at the start of the level? have a look around and you should see a catapult along with a tree of snowballs. it the tree with a melee attack to knock some off, then push one to the catapult. hit it with a melee attack to launch. After 3 shots with the catapult the barrier will be destroyed and you can move on.