Article: The easiest place to do this is level 2-1, the first level of Donut Plains. Jump on the "super koopa" with a flashing cape at the very start of the level. Collect the feather that pops out to get the cape. The cape win is usually used for speedruns or just for fun. Since you need to keep the cape power-up the whole time on your way to Bowser, the normal method above is usually easier. . When you have the cape, you can launch yourself into the air by pressing B while Mario is running. The more speed Mario picks up, the higher you'll go. To keep flying, hold the B button and alternate hitting the left and right arrows of the D-pad to rock Mario back and forth. Press forward on the D-pad to make Mario dive and pick up speed, then press back to use this speed to ascend higher again. Practice this until you can stay in the air for any length of time without falling. You can also use these moves:  Use X or Y to spin around, knocking objects and enemies next to you with the cape. Spin jump with A while Mario is running at maximum speed to launch yourself very high. Glide down slowly by holding A or B. This is the second level in the Valley of Bowser, and it contains a secret that lets you skip most of Bowser's Castle. (This will make keeping the cape power-up easier.) Play through the first two screens as usual, until you enter the second pipe. If you lose the cape early on, you can get it back. Right after you enter the second screen, jump up the steps to your left and look for a hidden block up near the top left corner of the stage. On the third screen, the pipe spits you out in the middle of the moving yellow "maze." Jump through this quickly, and you'll soon reach a gap with a mole in it. At this point, use your cape to fly up through the top of the screen, and go left. Walk left across the top of the stage, and you'll fall into a room with a secret door leading to a secret level, Valley Fortress. Most of this level involves timed jumps or movement to run through skewers, or to avoid spikes that fall from the ceiling (which are a slightly different color from normal spikes). Once you beat this level, and the familiar fortress boss at the end (Reznors), you'll unlock the secret Back Door level.  You can get a cape here as well. Hit the green block right after the first set of skewers.  You do not need to keep your cape to beat this level. The Back Door skips over most of Bowser's Castle, and does not add any new challenges. Just make sure to keep your cape throughout this whole level if you want to use it for the boss fight. The cape makes it easy to avoid most of Bowser's attacks by flying over him, and allows you to spin the cape to stun the mechakoopas. The fastest way to defeat Bowser using a cape involves jumping on him from above, timing it so you land on a mechakoopa right as he releases it. This can take quite a bit of practice and precise timing.

What is a summary?
Get the cape power-up. Practice flying Enter 7-2. Unlock Valley Fortress. Beat Valley Fortress to unlock the Back Door. Beat the Back Door to reach Bowser. Defeat Bowser using the cape.