Let's start by wiring our LED. First, secure the LED to either a pair of helping third hands or a panavise - this will help us keep the LED sturdy while we solder wires to the legs.
Silicone Cover Stranded Wire
I highly recommend using silicone cover stranded wire for this project because it's flexible and won't break under stress. Regular wire wrap or PVC cover wire is OK but it could potentially break over time.
30AWG size wire works great here because it's thin and strong enough for the longevity of this project.
OK, now we'll need to figure our how long our wires need to be. This all depends on what your attching the unicorn horn too – Will it go on a hat? hoodie, bandana? All will require different wire lengths. A good rule a thumb is to use a bit more than you need, because it's easier to trim it down and to add more later.
Once you have your wire length figured out, cut two pieces out (both in the same length) and use a pair of wire strippers to remove about 5m of insulation - exposing the bare wires. You'll need to do this for both ones, on both tips.
It's good practice to tin your wires before soldering them to anything – Tinning is the act of applying a bit of solder to the exposed wire, effectively "glueing" the strands together to prevent them from fraying. I recommending using a pair of helping third hands to all of the wires together while soldering. It's much easier to do them all at the same time like shown in the photo.
Most LEDs will have long legs. This is great for prototyping on breadboard, but we won't need them this long, so let's trim them short – But not before noting which is positive (anode) and which is negative (cathode). The longer led will be the postive anode, while the shorter one is the negative cathode.
It's also a good idea to tin legs of components, not just wires. Now that the legs of our LED are shortened, apply a bit of solder to them. Again, this is really going to make it easier when we solder our wires to them.
Solder Wires to LED
OK, now it's time to solder our wires to the legs of the LED. Here, I soldered the red wire to the postive anode, and the negative cathode to the blue wire. It doesn't really matter which color you use, but it is nice to keep it consistent with the electronics standard.
Tin Pins on JST Switch Breakout
Now it's time to get out our JST switch breakout. Before we solder wires to this, let's tin the pins! Apply a bit of solder to the SW and GND labeled pins on the JST switch breakout. I'm sure you know by now why it's a good idea to tin these pins ;-)
Solder Wires to JST Breakout
OK, now we can solder in the red wire (positive anode) to the SW labeled pin on the JST breakout and the blue wire (negative cathode) to the GND labeled pin.