How do I know what power supply to use with a circuit?
The board can be powered via USB, so the 5V adapter is OK.
The required voltage of 3.3V is generated on-board from the 5V supply. The maximum voltage for the inputs is 3.3V.
You can find the datasheet here: https://docs.particle.io/datasheets/photon-datasheet/.
In general you should try to find the specification. You can also look at the schematics and the specification of the parts.