How to fix Mountfield MPR10071 - Clutch/Gearbox Tension Spring ?

I have a Mountfield Laser Omega Self-propelled Petrol mower - 46cm, model MPR10071. The spring from the clutch or gearbox is hanging off (situated at the rear right side of mower when facing it) and I cannot see where the end that is hanging attaches. The spring is called a tension spring and I assume it is has something to do with keeping the tension of the drive belt as this keeps slipping off. The drive belt is in good condition. Please could someone explain in simpliest terms how and where to attach the spring?
Thank you.