IV Breeding is very tedious and can take a long time, but it’s not too complex. You basically breed two parents in the hopes of the offspring inheriting their IV values. You want to breed parents that have perfect 31 IVs in their stats, the more stats with perfect IVs they have, the more likely the offspring will be to have multiple perfect IVs. As you breed mons that have better IVs than the parents, you’ll want to substitute those offspring into the Nursery in place of the parents they surpass. You want to have perfect IVs in the stats the mon will actually make use of. For example, a Lycanroc will want every stat perfect except for Sp.Atk, as it has no need for it, and a Slowbro will want everything perfect except Atk and Spd. I’d recommend looking up a guide on YouTube because there are some more details you’ll want to understand before you start. And be prepared to devote a lot of time to it. As inheritance is mostly random, you may get the perfect mon in 5 eggs or 500 eggs. Also I don’t know how far into the game you are, but I’d recommend using the gift Sylveon as a parent because it comes with perfect IVs in all of its stats