So let's look at how to breed animals. As you can see I've spawned a bunch of sheep, and I'm holding some wheat. And once I'm holding that wheat all these animals want to be my friend. They are following me around. So, to get their attention, hold the wheat. And to breed them, just click them with the wheat, and they'll start bumping and grinding, and baby animals will start to appear.
Alright, so, this is too many sheep. But as you can see, I have some dogs here, and you tame dogs, if you don't know, by giving them a bone or multiple bones until they're tame. And to breed dogs, you give them meat. Because they're dogs. So get them up, and they'll start bumping and grinding as well, and baby dogs will come out.
And it looks like the baby dog will automatically be tamed. There you go. So that's how to breed animals. Pretty much every animal works the same way. I don't think you can breed slimes, but that's it.