Powering the Arduino Mega with a Lithium Battery

Step 2 Connect the wires into the Lithium Backpack

At the top of the Lithium Backpack is a 4-pin female header. On the back of the Lithium Backpack is 4 small markings that tell you what pin is what. There's a 5 volt pin, a 3.3 volt pin, a ground pin, and a status pin. The status pin outputs a 0-5 volt signal, where 5 volts means the battery is fully charged.

Connect one of the two wires you have into the ground pin (in the picture, the blue wire), and the other wire into the +5 volt pin (the red wire).