Those little ends should have small spikes that stick into the wire. Those little spikes make contact with the copper wire inside. You then shove the ends attached to the spark plug wire into the boot. You should see the little metal cup fully seated in the boot open when properly seated.
This YouTube video is not exactly what you have, but it should give you general idea.
Some people like to expose about 1/4 inch of the copper wire and bend it back on the spark plug wire. Then apply the crimp attachment for better contact. Then insert it into the boot as previously mentioned.
https://youtu.be/bEg63iRdjH4size
This is not my video, but random one i found on YouTube on the fly.
