If you check out this thread ...maybe my other one? I have explicit photos of that very part of the assembly.. but, here you go.
There should be a solid brass rod and a sleeve. The rod fits in the sleeve and should be long enough to hang out one side. There are some smaller brass hitting that came with the kit, they fit into each other then the small sleeve should slide onto the solid rod easily. After making sure they fit pull the solid rod out and slide the small spring onto the solid rod behind the retaining sleeve...insert the rod into the brass sleeve and it should have a springing action to push the pin you will make on the front of the rod into the hole in the body where the thumb release screw inserts. Once you know how deep the pin needs to be super glue it in place and file the edges til they are rounded off..you have just made the release pin mechanism for the cylinder... again, check my photos on my last build I believe there are good photos in there! Hope this helps...cheers!