From Bunni Wiki
Just a mouse, not the one with whiskers and ears.
Click and hold the mouse button to move your character.
Click on a bubble to add it to your inventory. Once you have something in your inventory, click on it and drag it to where you want to use it. Don't worry if it's not exactly where you want - eventually, you'll get bombs which let you blow up what's there and turn it back into a bubble.