Instructions
Place the Epic Mickey disc in the Wii, and attach the Wii nunchuck to the remote. Choose "New game" from the options.
Watch the animation featuring Mickey to learn the background of the story and see how he is sucked into Wasteland. Mickey will wake up in the Mad Professor's laboratory inside of the first game level, Dark Beauty Castle.
As soon as the animation finishes, explore the Mad Doctor's lab. You will find Gus the Gremlin waiting for you on the second floor. He will tell you how to launch a spin attack by shaking the Wii remote.
Use the Mickey spin attack to break both robot control panels on the second level. The first is right next to Gus, the second is off to the far right. You'll have to jump across a small opening to reach it.
Meet Gus the Gremlin again and he will show you the utility corridor. Pass through the corridor and complete both the paint "A" button and the thinner "Z" button tutorials. When you finish both tutorials, your paintbrush will be active and you can exit the castle and get started on your epic adventure through Wasteland.