To power the circuit, you need 4 batteries of 1.2V, AA or AAA size or 3 batteries of 1.5V (AA or AAA size).
Using the blowout candles is easy. Of course you need a cake to be able to use the candles :).
We organized a fictitious birthday party with a virtual cake to celebrate the project and a video of that party and the birthday candles
If the video isnt working, you can try this youtube link: Birthday Candles Video