If you'd like to plug in something that can power from a USB port, the included USB connector will do the job!
You will need to solder it in place, however. Press-fitting wont work!
Snap the USB connector in so that all of the pins go through the PCB. Make sure you're solder them on the back of the PCB
The PowerBoost 1000C does not come with an on/off switch for the output, but its very easy to add one! Just grab a Breadboard friendly SPDT slide switch from the adafruit shop.
We will be turning the boost on/off via the ENABLE pin, so the switch does not have to carry any power, it is only signalling to the boost converter what to do. This means the switch can be small. Use any switch you like, if it is 0.1" spacing thats ideal. If your switch only has two pins instead of three, tie one pin to GND and the other pin to EN - when the switch is closed, the power will turn off
The switch will go into the breakout header, and attach to VS EN and GND
The switch is symmetric so as long as those three pins are attached to the switch you are good to go
Before soldering, check that you have the right three pins!
I used some tape to keep the switch in place while soldering