It has been a couple of years since I put mine in, so I wish I could help more, but I remember being a little frustrated also. Here's the other page of instructions if it helps. I believe you need to punch that plunger out so you have a hollow tube. Then you take apart the tampon looking thing and insert in the tube like is explained in the directions. You may need this install kit depending on your wheel. This one is for 70-72, there is another one for 60-69.
https://www.classicparts.com/1970-73...nfo/32%2D493C/
Hope this helps.....