how do you use it?

OK, I had to make sure it was the same style as my old one has.
You use it by hooking the one part under the edge of the can like you would hook a bottle opener under the edge of the cap.
Then you put the pointy part on the lid right next to the rim and pry to punch a hole. You then simply keep making the hole longer instead of punching another hole.

The opener really works well, about as fast as one of the Swing-away ones you twist the side handle to use.

The Swiss army opener works almost the same way except it cuts away from you instead of towards you.

And you bring it towards you each time you get a bite of lid, don't go forward with it...