The chain should be regularly cleaned and lubricated. We recommend cleaning the chain first with a bicycle-specific degreaser and cloth. On bikes with a hub gear, the indicator gear should be lubricated where it exits the rear axle. Start with a clean and dry chain. Apply a few drops of chain lubricant to each roller
N.B The build-up of dirt can clog up the drivetrain and cause excess wear. When oiling the chain, a little goes a long way.
You can watch how to lubricate the chain here.