There are only a few ways that the chain can be tightened.
Garage door chain drive adjustment.
You will have to apply a spanner to each and turn them in opposite directions.
Usually a pair of nuts are associated with the locking mechanism while one is concerned with the adjustment of the chain.
Chain adjusts by shortening the chain itself.
There may be an adjustment linked to the chain or an adjustment to the length of the door opener track.
Use the wrench to loosen the lock nuts and turn the adjustment nut to set the slack in the chain.
Both adjustment types should be done with the door closed and disconnected from the opener using the emergency release.
Loosen the two lock nuts on the threaded rod.
If you stand at the door facing the motor you will probably see the threaded rod that adjusts the chain length on the right side of the door.
Adjust the chain on a garage door opener with help from a garage door spec.
The chain is a very important component that makes up a garage door opener system.
On the master link you will see two or three nuts.