Start off Dream World by heading forward, toward the second goblin arena. Equip your walking-stick at some point, so you can get a long-jump in after the first set of stairs.
Once you reach the second goblin arena, you'll be doing a slope-boost to hit a cutscene trigger, which will end the level:
Alternatively, if you're having trouble with that method, here's a slightly easier method that involves climbing a tree to get out-of-bounds: