Grab your coin cell battery and press one lead from each end of the n00d to opposite sides of the battery. If it lights up, bingo! The side pressed to the + side of the battery is your + lead. If it doesn't, flip the battery around and see if it lights up when you test it the other way.

Keep track of which end is + and which end is -.

Cut a piece of wire long enough to go from your planned battery location to where you want the n00d to lay out. The wires can be trimmed later, so err on the side of "too long." Strip about 1/4" of shielding from the wire.

Place the wire and n00d lead next to each other as shown. Twist the bare wire around the n00d lead a few times so they're solidly connected.

Solder the wire and the n00d's lead together and give a tug to make sure you have a solid connection. Pull the wire away from the n00d to get a straight line without bending the n00d's lead -- let all the bend be in the wire. The leads are delicate and you're less likely to break them this way.

Cover the connection with heat shrink. 

Solder another wire to the other end of the n00d. Remember that both ends need to be connected to the power source so make sure your wires are long enough to reach all the way back to the battery.

Test again with your coin cell to make sure it's all working.

The n00d will connect to the coin cell breakout as shown: the + lead (red wire) goes to the Sw pin and the - lead goes to the Gnd pin. 

However, if you're planning to weave your n00d into your mask, don't solder it to the battery holder just yet. It's much easier to decorate the mask when you've got the ends of the n00d free, and soldering it all together at the end will allow you to trim the wires to exactly the right length.