Boys, boys, boys-- There are different models you can use. Some go just around the cock. Some go all the way down to the base, so that both your cock and balls are through them. When it comes to first experiences w/ metal cock rings, bigger is always better. I prefer the ring that goes around everything. You start out with a flaccid cock. Slick everything up with your lube of choice (saliva, KY, baby oil, etc). Slide one ball through the ring, then bring the ring up close to your body and push the second ball through the ring. At this point, you can check correctness of size. If you release the ring, it should hang on your scrotum, held up by your balls, but not be painful at all. Next slide your well lubed mostly flaccid cock through the ring so its in contact with your balls. You can push the ring up a little closer to your groin at this point, and give a few happy tugs on your cock. It should all feel snug and comfortable. If you feel any pain at all, get some cold water on your cock and reverse it out of there the way it went in, pronto. You may need to start with a larger size ring. Better that than a trip to the ER with a potential embarassing (and worse, cock & balls threatening) emergency! As your cock fills with blood, the fit will get more snug. You will probably feel more of a fullness there, the color of your skin will be darker, and surface veins will be way more prominent. Share your new and improved cock with someone you love. Your cumshot will probably not go as far due to the restriction at the base of your cock, but volume should be unaffected.
After ejaculation, as your hardon subsides, remove your cock from the ring first, then the balls next, one at a time. You may need a little more lube to get things out, but I doubt it. Enjoy! I've been ringin' for about 10 yrs now, and I definitely enjoy it.