To connect the LED Strand to the Gemma M0 board, you'll need to do a little prep work first. Basically, you will disconnect the attached battery holder and expose the metal part of the wires. When you attach it, its power will come through the board, which requires its own battery holder.
In the step that follows this one, you'll find some options for attaching the Gemma to the large alligator pads.
Detach the Battery Pack
If you want to test the LED strand, insert the coin cells into the holder and turn it on.
Be sure to remove the batteries before going further!
With scissors or wire cutters, cut off the attached battery pack.
If you leave a couple of inches of wire attached, you can save it for some other use.
Prep the Wires
There are two wires going to the strand of lights, connected by a soft plastic coating.
Grab the cut ends of the wire, and carefully pull the wires apart for 3 or 4 inches.
Strip a good half inch or so of the plastic insulation from the end of each wire to expose the metal wires inside.
To keep the bunch of thin wires together, give them a twist.
Test and Mark the Wires
LEDs are polarized components, meaning they will only work if the positive wire is attached to the positive side of the battery and the negative wire is attached to the negative side. So next, you need to figure out which is which!
Take one of the coin cell batteries and pinch it between the two wires. Make sure each wire is only touching one side of the battery, and don't let the wires touch each other!
When the lights come on, make note of the wire touching the positive (+) side of the battery. Mark it with a pen or piece of tape.