You can power it using either a USB phone charger or some other 5v power source.
It can supply 2A at 3.3V or 0.75-3V. You can use a jumper to switch between either a fixed 3.3v output or a variable output from 0.75-3V which you adjust with a trimmer potentiometer. Using the switch you can bypass the voltage regulator and pass thru the 5V from either the USB port or your 5v power source.
The power supply has output pin headers so it can be used on its own, in case you want to use it with other projects.
There is a footprint for an optional input capacitor that you can install if it is needed for your particular setup, it uses a capacitor with 3.5mm lead spacing and an 8mm diameter like this one.
Make sure to change the voltage before connecting anything to it to prevent damaging whatever you connect to it. When using it with the FlashcatUSB xPort use only the same voltage as it, so either 3.3v or 5v.