The process is fairly simple. You place the bottom (signified by the hole in the center of it) set tool in a vice, or other rigid surface that will hold it in place. Next you position the rivet or eyelet into the hole, and place the already rounded side down into the bottom tool. You will feel it when it clicks into place. You can also look down through the eyelet, and watch for the hole in the bottom piece to help you line it up.

Next you take the upper tool, the one that has a protruding knob in the center, and place it into the unfinished end of the rivet. a number of taps while keeping the tools directly in line with each other will flair the rivet or eyelet properly.

Use the right size set tool for the eyelets or rivets you are installing.

Each tool is designed to cradle one size or another, and using the wrong size will leave you with this second image on the right.

Watch out for the ones sold at craft stores, they are often fine for small craft eyelets, but will not work on the larger eyelets designed for KYDEX® sheet.