changing out steering wheel- how to mount horn pad?

Hi everyone, looking for some advice/ help
I have a 1970 Dart Swinger i bought in 2020 which has a broken rim-blow steering wheel. Has never worked and previous owner mounted a house doorbell-type button to work the horn. Im trying to replace the whole setup with an original-style steering wheel/horn ring like the one pictured that could also be ordered for a '70. I bought a used mounting kit which I thought would have everything I would need to mount the used horn pad/ ring I found on eBay to a new reproduction steering wheel I purchased (the PG Classics repro). My trusted mechanic is having a hard time mounting the horn pad correctly, he thinks I may be missing a piece. I cannot find installation instructions or a diagram anywhere online and the factory service manual doesnt show any detail. Looking at the attached photos, are there any parts missing? Can anyone direct me to some clear instructions or diagrams that show the correct way to mount everything? Unfortunately Im changing
steering wheels so I cant just put things back together the same way. Any advice/ help would be greatly appreciated!