Head right to jump across to a sinking vertical ledge, and then you should
jump across to the next sinking vertical ledge before hopping to the solid
ground on the right (be sure to avoid the Podoboo that inhabits the lava pit
here).

Now take the bottom route, jump up to the next ledge you come to, and then
jump up to the next ledge as the one you are on runs out to get to the next
section of the castle.

Take a running leap to hit the high ledge the Firebar guards (just run and
jump as the Firebar will not hit you), and then drop to the floor first
chance you get. Now you should jump onto the next ledge immediately, and
then you should head right until you see a high path and the low path (take
the high path to advance).

Now you will see Bowser's flames start to come at you, so make your way past
the five bunkers in the floor to find the bridge. Now, go onto the bridge
to see a Podoboo guarding the King of the Koopas.