To fix the connecting rod to the crosshead, thread the pin through the rear of the rod, a paper washer, the rear of the crosshead, and solder the pin to the front of the crosshead (with the drop link on top if required). Remove the washer after soldering and cut the pin to length. It would look better if the pin head was on the front, but then you would have to solder at the rear of the crosshead where it’s more difficult to get the iron in. Repeat for the second set, but ensure you end up with a handed pair!
Spare pins are LS92.