Adjusting the ram is actually pretty simple.
Unscrew the knob from the pull pin. Then take the backplate off the gun making sure not to lose the little spring that lives behind it.
You will see the ram in the right lower tube.
They provide a tool which has 2 pegs to adjust the ram, but circlip pliers do just fine.
With air in the gun rotate the ram clocwise. Screw it a small amount, then try to open and shut the breach. Repeat.
Keep going until you have set the ram so far forward that the breach wont open/close.
Then back it off a little so its just possible to open/close it.
Edit to add, After you've set it you should dry fire the gun once or twice, and re check the ram adjustment. Just to make sure its staying where you put it.
But DONT fire the gun without the breach pull pin in place or you will wear the bolt.