You will find that this star is located near the bottom of the level, in an area you might have not have seen normally. When you begin, take the teleport at the broken bridge behind you to get to the bottom of the level, then mosey on over to the ski lift. There is a small island that has a Bob-Omb Buddy on it located in the middle of the ski lift’s journey that might be a little difficult to get to otherwise. Once you reach the small island, speak with the Buddy to open the cannons, then return to the bottom of the mountain.
There will be a cannon right near the ski lift, so get in it and look for the lone tree that is underneath in the distance. Remember that you have to aim higher than usual to account for Mario dropping while in the air, so put your reticle so the bottom arrow lines up with the corner of the blue-gray land to the right. If done right, you should grab the tree while flying. An alternative way to reach this area down here involves a Spindrift enemy. In the area with the snowman on a pedestal, you should see a Spindrift close to the edge. Jump on it and you can float down to the section below it, as long as you don’t bonk on the one wall above it.
However you get to this area, follow the only way you can get, getting rid of the two Spindrifts along the narrow ledge. Past them, you will have to Long Jump past a gap, then you will be in the area with the star. It is on a ledge above your current position, and you will need to perform some Wall Jumps to get to it. Go to the right side first and you only need a normal jump and a Wall Jump to get to the next ledge. For the second one, though, you will need to perform a Triple Jump before the Wall Jump, but third jump will need to be closer to the left edge.
The reason for this is because there’s a slightly slope underneath the wall you will be jumping off of, so you don’t want to hit the slope. Thankfully, there is ground below you and should you take fall damage, there is a spinning heart you can use to restore your health. Keep trying and you will eventually reach the top. Once you do, if your camera is at the furthest viewpoint, move it closer and turn it so you have a good view of the icy path leading to the star.