I tried to find you some videos/animations. The problem is the T92 is a sliding mesh transmission and everything I found that shows the shifting mechanism is a synchronized transmission. While the operation is very similar I was concerned that the synchronizers (which yours doesn't have) make it look more complicated than it is.
Bottom line - get the tractor set up as MNGB suggested and play with the gears.
Some background that I hope will help you get started:
Your transmission is essentially two simple transmissions in the same box and each one can select between two ratios and neutral. Each simple transmission occupies one side of the H in the shift pattern. The left side does Reverse, Neutral, 1st. The right side has 2nd, Neutral, 3rd. It's pretty plain that at least one of the two transmissions needs to be in neutral or the gear box will lock up. This is supposed to be prevented by only allowing the shift lever to cross the H when the transmission it is leaving is in the neutral position. In your case the wear on the end of the lever let it cross when it shouldn't have and you locked it up.
The shift mechanism attached to the cover operates the transmissions via the forks that hang down from it, the rings they engage are easy to see in your pictures. The front transmission is the 2, N, 3 and the rear is the R, N, 1.
I think it's going to be pretty obvious where to slide the gears of the front transmission to achieve neutral. I cannot tell from the pictures exactly where to position the rear to get neutral there. What I suggest is you put the front in neutral then if the rear isn't obvious play with it as MNGB described to find neutral.
Then experiment with it, moving the gears by hand, until you understand how it all works together. HAVE FUN!
Edited by MiCarl, January 01, 2017 - 10:54 AM.