As the name of the star points out Huge Island, that is the painting you will be going in at the start. Your goal is to pretty much get to the top of the mountain, where the star will be waiting in a yellow box. From the beginning of the stage, go through the doorway and begin swimming through the water on the other side. You will want to keep swimming straight here, making sure to avoid the Lakitu throwing Spinies, as well as the Bubba that will try to swallow Mario whole. At the far end, get on the grass and Long Jump to the next platform, where some wind will begin to blow.
The next ledge is a little tricky to get to, as the blowing wind will keep pushing you away. You will want to Triple Jump straight towards the platform and although it’ll look like you won’t make it, a sudden updraft should carry you onto the ledge. Once you’re there, follow the path before you until you reach some Big Steelies rolling down the mountain. When you finally reach the point where you find the source of them, you will have two different ways to go. For now, you will want to go up the hill, so jump to the next section, where you find a Grand Goomba.
Ignore or take it out, then jump to the next ledge and then to the final one, which will have a Chuckya moving about. Quickly run past it or pick it up, as you don’t want to be thrown off by it. The only way to go from here is via the wooden walkway, so be careful while moving on it, then go up the hill at the end to find the yellow box with the star.