Grab your on/off switch and JST connector. Cut the red wire in half. Trim the switch leads a bit, if desired, and solder one side of the red wire to each leg of the switch. It doesn't matter which leg goes to which side. Heat-shrink tubing over the connections prevents electrical shorts…remember to slide this on the wire before soldering.

Cut the female connector off the end of one of your LED strands. Hook up the three wires to your tester. On my strands, the left most wire (with the resin bump on the LEDs facing you) is power, the middle wire is ground, and the one on the right is data. 

It's very important to test these and make sure you have the connections right. These strips are not marked in any way, and we've gotten inconsistent wiring with different lots, so testing is essential. If you can't get the lights to come on, play around with different configurations or try connecting data to the other end.

Here is a guide showing how to set up your Circuit Playground Express as a tester using MakeCode.

Once you've established your wiring, it's a good idea to mark the wires with some heat shrink or tape so you keep them straight.

Strip a generous 1/4" of shielding from each wire. Do the same with your second strip and twist the wires together: power to power, ground to ground, and data to data.

Hook both wires back up to your tester and make sure they're both working.

Make two more twisted pairs of strands with your remaining four LED strips. Cut four short wires for the next connection: red for power, black for ground, and two colored data wires.

We're going for a set of two strands and a set of four strands. The two-strand set will become the tentacle lights, and the four strand set will become the lights on the top of the jellyfish.

Twist two of your twisted pairs together to form a quad. Solder a red, black, and colored wire to the power, ground, and data clusters. Cover the connections with heat shrink.

Do the same with the remaining twisted pair.

Let's keep consolidating wires! Twist the power and ground wires from your pair and your quad together and solder on another single red and black wire.

Leave the data wires separate. 

Twist another short red wire and black wire onto the JST connector and power switch as shown. Solder the switch's red and black wires to the LED strand cluster's power and ground wires.

You should be left with a whole mess of wires that are soldered together, and four wires left unconnected: a power wire, a ground wire, and two data wires.

Finally, we'll wire up the QT Py. Red goes to 5v, black goes to G, the quad data wire goes to A0 and the pair data wire goes to A1.

If desired, trim the connectors off the other ends of the strips. You can seal them up with some heat shrink to keep them safe from moisture or shorting. 

Or, you can plug in another strip to each one and make very long jellyfish tentacles! It's easy to add more lights with these strips. Just remember to change the strip length in your Config page on WLED.