From the Super Mario Wiki
The player starts off by landing on a Goomba and getting a + Clock, they must then proceed up this area and then go across some metal platforms that have some spiked cylinders on them. After this, there is a platform that is propelled into the air by lava, and then a small castle segment that leads to some more metal blocks. The metal blocks lead to a platform with two Goombas on it, and some more metal platforms on the left which lead to some more platforms. After these platforms, the Dry Bowser battle starts, the player needs to hit the switch at the end of the course to defeat Dry Bowser and then use the Warp Box to reach the Goal Pole.