Well i would assume it's the same as any other sniper rifle in basics:
-Detach the trigger/receiver/barrel assembly from the stock.
-You may or may not have to remove the cylinder depending on model- I would anyway
-There should be a screw on the underside of the receiver where the barrel joins it.
-Loosen the screw
-Twist the barrel (normally anticlockwise) along it's horizontal axis until it detaches.
-You now have the outer barrel.
-Use some implement to push the hop-up chamber out of the barrel towards the breach (rear of the barrel)
-Pull the hop-up chamber out, with the inner barrel attached.
-Open the hop unit- inner barrel and hop rubber are detached
-Clean everything
-Reverse process