The circuit to create and amplify the sound isn't trivial, but it's made of simple building blocks. I'll show you how to build a light sensor with a CdS photoresistor, a simple op-amp preamp, an oscillator with the classic LM555, and a 5 watt power amplifier with the LM1875.
You can do it if you follow the instructions, I'll try to explain the details.
Step 1: Stuff You Need
A candle and candleholder.
Wire - I like to have around two 3-packs of wire from radio shack, one solid core and one stranded. I prefer 22 gauge.
Perfboard - I like the board number 276-150 from radio shack, it's cheap and useful.
Power supply - I designed this with the Mean Well 24V 1A wall wart from Jameco. You'll need one of the corresponding jacks also if you don't want to solder the supply directly to the board.
Electronics components - You can get all these from Jameco.
1M Audio Taper Potentiometer
Photoresistor (I used Jameco #CDS003-7001)
MC1458 x1 (Any general-purpose dual op-amp is fine, these are cheap)
LM1875 x1 (plus heatsink)
1N4733 x1 (Any 5V Zener diode is fine)
8-pin DIP sockets x2 (DIPs are hard to remove if you blow them up accidentally, best to socket them just in case. The LM7805 and LM1875 are in TO-220s, easier to pull out of your board if necessary..)
Soldering Iron & solder
Pliers, wire strippers, diagonal cutters