Courtesy of Adafruit Industries
While there is a pile of builtin hardware, it doesn't include everything. Fortunately it does have several useful connections run out to the alligator clip pads around the edge of the board. That means you can connect to it using alligator clip jumpers, like one of these:
Trace the outline and hole placement of the CircuitPlayground onto a piece of prototyping board, then carefully drill the holes to match those on the CircuitPlayground. This is a bit tricky with the prototyping board, but it just has to be close enough.
This prototype is mean to mount the CircuitPlayground onto a breadboard so put a couple 14-pin header strips in the center at DIP-14 spacing.
The next step is to add wires. Start by soldering them to the header pins on the other side of the board, clipping them so as to leave plenty of length beyond the holes.
Red for 3.3v & 5v, black for ground, blue of everything else. Mostly this was to make sure you know how everything was oriented when it comes time to mount the CircuitPlayground.
Once all wires are in place, strip the insulation off the ends, starting just inside the corresponding hole.
Bend the ends to go around the bolts that will eventually go through the holes. I found it useful to use a longer bolt of the same size (M3 in my case) to bend the wire around. Trim off any excess wire.
The next step is to mount the standoffs using a matching bolt, sandwiching each wire loop between a standoff and the board..
I used hex standoffs that take M3 bolts. It's a good size for this application and the hex shape makes it easy to grab when it's time to tighten things.
I used 10mm standoffs because I happened to find some quickly. For future work I ordered a bunch of 6mm ones since 10mm of space is excessive. You can find the spacers in various lengths. Just be sure to get bolts that are short enough to fit when screwed into each end of the standoff (keeping in mind the thickness of the board on each side.
Don't tighten them all the way; you'll want to be able to adjust them when mounting the CircuitPlayground. Put each bolt through a hole from below and screw the standoff onto it. Again, don't snug it up, just finger tight.
Finally add the CircuitPlayground board, using the remaining bolts. Once all the bolts are in place, tighten everything. If you used hex standoffs, it's easy to grab one with needlenose pliers while tightening the bolts on either end of it.
Now you can plug your CircuitPlayground into a breadboard and start building without worrying about clips popping off or wires getting pulled out.