How do you replace the chain on an older model concept 2?

To replace the chain on an older model Concept2 rowing machine, first, ensure the machine is unplugged for safety. Remove the chain cover by unscrewing it, then carefully detach the old chain from the flywheel and pull it out of the rail. Thread the new chain through the rail and attach it to the flywheel, ensuring it's properly aligned. Finally, reattach the chain cover and check for smooth movement before using the machine.