Click the green flag to begin, then click start. the button will enlarge if your mouse is on it, so make sure you're clicking it. Click on the buttons to pick flavors and toppings. Once you've picked a flavor and a frosting, a blue button will appear in the top right corner; click to finish. Click the flag to start over with a brand new cupcake.
Suggestions for flavors, toppings, and anything else are always welcome, so if you have one tell me in the comments :)