Now thatMario has his own ship, you’re free to explore the available galaxy as much as you like.
Your options are limited at first, and one of your choices is back in the Sky Station Galaxy: the "Storming the Sky Fleet" level.
“Storming the Sky Fleet”
This galaxy has changed slightly since you defeated Peewee Pirhana. Chomps now roam the area outside of Yoshi’s house, and you’l have to use your spin move in concert with the local rubbery vegetation to take them out. Line one up on the other side of one of the giant ball-shaped plants, then hit the plant with a spin to send the chomp flying. Line it up correctly, or else the plant will bounce back and hurt Mario.
Make your way around and down through the green warp pipe. On the other side, several chomps are moving in circles around more of the rubbery green plants. Use the plants to defeat them, and one will drop a key, freeing the nearby imprisoned Luma. You can also use the plants to strike the treasure chests and gain a free life or two.
Speak to the freed Luma, and he’ll transform into a launch star which you can use to get to the next area, a giant cylinder in space.
Storming the Cylinder
Avoid the incoming Bullet Bills as you run to the other end of the cylinder. You should see a metal hatchway marked with searchlights. Wait for it to open and drop inside.
Hit the nearby flag, then fall down through the rotating cylinder. Once you hit the long drop filled with star bits, you’ll want to head to the right to continue on. You can head to the left for a 1up mushroom, but then you’ll have to move through the cylinder again and fall to the right to keep going.
If you head down as you go to the right, you’ll find a teleporter which leads to a small platform with a star and some enemies where you can earn a few extra lives. After you’ve returned, hop on one of the upward-moving platforms. You should eventually see a launch star on your right. Time your jump to avoid the electric enemies nearby and use it to continue to the next stage.
The Board is Green
Hit the continue flag near where you land, then turn all the blue platforms green by walking on them while avoiding the giant Bullet Bill. Once they’re all changed, the next part of the level opens up. Don’t forget to grab the nearby 1up mushroom.
As you hit the first of the next series of platforms, Cosmic Clones will begin to spawn and chase Mario. Keep moving and hitting all of the platforms. Once they’re all changed the Clones disappear and a launch star spawns. Jump into it to continue.
Another flag awaits you as you land, as do several Bullet Bill cannons. Avoid the enemies as you follow the path and make your way to the right. You can use the handy bouncing plants to take out any Bullets that get too close, just make sure you time it right. On the far left of the end platform, three Phirana plants await you. The large one is your target. Use the nearby plant to defeat it and pick up the key to free the Luma at the other end of the bridge.
Hop down, use the plant there to take out an incoming Bullet Bill, then race across to the other side. Use the small ditch to let a Bullet pass harmlessly overhead if need be.
Once back across, grab the star there and your mission is complete.