Once you have your cable and source, simply connect them to the Nano. Your board will automatically receive a regulated 5V supply and power up straight away. That's all there is to it, really.

You can also go the 9v battery route plugged into the on-board regulator of the Arduino but the low mAh rating of a 9v won’t allow your project to stay running for very long.

You can use an unregulated external power supply with a rating between 6 and 20 volts, and connect it to the Nano's VIN pin on Pin 30. Often, the supply is a 9-volt battery, as it's portable and ...