Connect it to the 12v socket, allowing sufficient slack at the plug end, then navigate it through the spaces between interior panels and under the dashboard (utilising clips or tape) until you arrive at the door.
Proceed similarly down the side of the dashboard, then insert it beneath the A-pillar trim until you reach the upper edge of the windscreen. Subsequently, insert it under the roof liner to ensure the plug is correctly positioned.
If surplus cable exists, coil it and store it along the path, such as under the dashboard or behind the kick panel in the driver's footwell.