Your blinky badge kit comes with the following parts:
Pin and clasp
2 self-blinking RGB LEDs
CR1220 3 Volt battery
To assemble the kit, you'll also need a soldering iron, safety glasses, wire cutters, tweezers, and solder flux.
Attach the switch
The switch goes on the right-hand side of the back of the badge. The switch lever points outwards.
Tin the pads on the side of the switch. These pads are for mechanical stability. Don't use too much solder.
Apply solder to the three small pins on the back of the switch. These provide the electrical connection to the battery and LEDs.
Solder the battery holder
Place the battery holder over the large circular pad. The small metal 'nibs' of the battery holder go over the square pad. Make sure the 'open' part of the battery holder points toward the bottom of the badge.
Solder one side of the battery holder, then solder the other: