With this simple mod once your battery reaches a certain level, the battery indicator LED will start blinking for around 15 seconds every 1 minute. You can set the voltage at which the LED start blinks by shorting out the "Set" solder pads (e.g with a screwdriver or wire) on the board for 2 seconds when the battery is low. This product is mainly designed for LiPos as the LED indicator doesn't really dim when the battery is low. The default voltage is set to around 3.3v suitable for LiPos.
Connect 3 or 4 wires depending on the battery / output type and you're good to go. You need to supply your own wire. Check out the v1.1 installation instructions on the left tab.