Instructions
Find the character of Bottles in Clanker's Cavern, the third level of the game world. Bottles can be found after you jump into the blowhole of Clanker, the giant, whale-like machine in the cavern. He will be wearing an orange suit and resemble a mole. Talk to him and he'll teach you the Wonderwing.
Collect some gold feathers. These are scattered all over the game world. You can carry up to 10 at once, but no more than that. They don't replenish, either, so once you've used them up, that's it.
Hold down the "Z" button, which is located at the back of the Nintendo 64 controller, and simultaneously press the right "C" button (the four yellow buttons on the right side of the controller). Kazooie will shield Banjo with her wings, making you invincible to all enemies. Enemies will also be destroyed on contact.
Keep holding the "Z" button to continue the Wonderwing. Release it when you're finished to deactivate it. You can perform the Wonderwing for two seconds per golden feather, so the maximum of 20 seconds at a time.