Powering a ESP8226 via supplied breakout board
These breakout boards are meant to be used with a 3v3 linear LDO regulator, for which there is a place at the backside of the PCB. This makes it possible to power the board with 5V (from for instance USB).

If you have 3.3V available (note: with sufficient current: the 3.3V output of for instance a usb-serial converter won't work!) you can replace the regulator by a short of the two copper fields at the back nearest to the Vcc side (the 3d copper field is conected to the GND).