I'd suggest getting a book on it. David Chicoine's book "Gunsmithing Guns of the Old West", the newest expanded edition covers the Winchester and the Rossi, as well as about any gun you may want to use in SASS/CAS matches.
There is a screw on the side of the receiver, directly across from a hole on the opposite side. Removing that screw (which is a plug) allows you to drift the lever/bolt pin out of the frame (toward the screw side). You have to look down the hole to see when the hole is lined up with the pin, the lever has to be moved to position it.