Step 1: Materials
(NOTE: the board will come with a LiPo battery, several sewing needles, and two bobbins of conductive thread)
2. USB cable (you'll probably have a few of these laying around if you look - I used the cable for my Canon camera)
3. Christmas-themed sweater (I used this one)
4. Pair of tweezers to snap apart the board
Step 2: Uploading Your Code
Next, you want to copy and paste the code that I will attach here into the Arduino IDE. You will then connect your development board to your computer using the USB cable, and upload the code onto the board.
This code includes four different songs. For whichever song you want to play (I ultimately decided on "Deck the Halls"), change the tune number of that song to "(tune == 1)". "Jingle Bells" is the default.
NOTE: if the music playing drives you nuts while the board is connected to the USB (I know it did me!), then locate the loopSong variable and change it from "true" to "false". Then just change it back to true when you're finished.
Step 3: Sewing Your Board
Now you need to locate where on your sweater you would like to sew your various parts. I like symmetry, so I placed two of my LEDs at the top of the sweater and two at the bottom. The board and the speaker are hidden by being sewed inside the sweater. You need to design your layout before sewing so that your positive threads don't touch your negative threads.
Now, using the conductive thread included with the Lilypad kit, sew each pin on the board to its corresponding positive pin on each LED and the speaker. Once you've finished with that, you'll need to sew one negative thread that starts at the negative pin on the development board, and then connects to the negative pin on all four LEDs and the speaker.
NOTE: I'll include a diagram of my layout once I get the chance.