The chain on my garage door opener came off. I put it back on, but it appears that it is not set at the right height. When I close it, it will not stay shut, and when I open it, it does not go all the way up. Is there a way to manually turn the gear that the chain is attached to so that it can get to the proper height?

Also, is there anywhere to download the user manual for this model? I inherited this opener when we bought this house and have no idea where the user manual is. Thanks!