Welcome to the forum!!
Look the winch itself over carefully and find the manufacturers name. Look for a model number on the winch then hit the internet. I bet a dime you can get a manual for the winch online somewhere. Some winches have a friction brake the locks when the drum is pulled backwards slightly by a load. Others have a ratcheting pawl that locks into teeth on the cable drum. If you or someone else doused the friction lock with oil or WD-40 then you will accomplish the same result as lubricating the brake pads on your car.
2006 23B Hybrid with 10k round bar WDH
2011 F150 4x4 SCREW Ecoboost, Max Tow, Integrated TBC, 3.73 LS axle, Firestone Ride Rite airbags.