TIP: Remember to put the plug cover on the wire BEFORE you solder everything together. Then slide the cover down and over the soldering.
TIP: Don't forget to have everything disconnected while you solder!
Solder the positive and female lines to the female plug.
Double check you didn't wire the board power to the stepper power. That would be bad.
Do you have a multimeter? This would be a good time to check your connections.
Plug in the power. The +5v light in the corner of each board should light up.
Now the wiring is done, time to test it with some code.