blimey thats an old model you are trying to user
roud:the wierd spring attaches to the spark plug and the other end to plug lead on no 1 cylinder,on left of the gun is a clear prism where you attached the cut out from box casing like a graph when the tick over and timing is correct the prism throws out a line to match up on graph that is inserted into the slot,this tool was used on cars with points and condensers from the dodo period,not on the new cars with electronic ignition:Clap: