Oh the strange paradox of jizz removal! Honestly the best way to get semen out of fabric is not to get semen in fabric, but I guess you can’t put that toothpaste back in the tube, so to speak. So. You might think the best thing to do is wash your sheets (or whatever, I neither want nor need to know) in hot hot hot water, because that is what you do with underthings and other smellies. But heat will coagulate the proteins in semen and actually set the stain permanently.
Instead, you want to rinse the item(s) in cold water, scrubbing at the spot. If the stain is dry, scrape off the crusty bits first. After scrubbing, you can soak it in cold water and a stain remover like Oxyclean. The internet suggests an enzyme cleaner, i.e. the stuff you buy to remove cat pee stink. Nature’s Miracle is the kind that I have used on my cat-related stains and it did a naturally miraculous job, but I have not tried it on jism.
After the visible parts of the spot have been removed, wash the fabric normally. If you’re talking about a dry-clean-only object, it is apparently correct to tell your dry cleaner that the stain is egg white. Which, if you are the sort of person who can hand over a garment crusted with your most intimate juices and tell the recipient what you both know to be a bald-faced lie, because who has ever spilled egg white on themselves, then vaya con dios. I don’t think I could bring myself to ask another human being to clean up semen for me. Let your conscience be your guide.
Now, if we’re talking carpet or upholstery, that’s a different matter. The surprisingly non-squeamish stain-guide.com has a fairly extensive entry on jizz removal, and for furnishings they have two suggestions. The first is to scrub a baking soda-water paste into the stain until it lifts, then wipe off the paste with a cloth soaked in cold water. Repeat as necessary. This treatment is to be followed by a baking soda sprinkle that sits for an hour and is then vacuumed up (for odor removals? Eek).
Their second suggestion is to scrape away any scrapeable bits, then blot blot blot with a cold-water-soaked paper towel. Just blot blot blot. Keep blotting. Blotting never really seems to do anything. Keep at it. After you give up on blotting, mix some dish soap or dishwasher detergent (designed to break down proteins, after all) with cold water and yes, blot that into the stain. Blot blot blot. Blot forever and never stop blotting.
Conversely, you can just throw whatever it is away, buy some wipes, and promise to aim better next time.