As I said yesterday, if you just want them to spawn as an interesting behavior, you can leave them where they are. However, if you want to raise the babies, you'll need a separate tank dedicated to this purpose. If the clowns are in your community tank, you might be able to set things up so that they lay eggs on a piece of tile or something that you could remove to a separate grow-out tank. I think you might have to have the parents with the eggs until they hatch, then take them out so they don't eat the babies.
I think ocellaris are among the easiest to raise, but you have to be prepared and dedicated to get them to survive and to avoid abnormalities that can result from poor water quality at various stages of the process. It's a challenge to keep them fed and keep the water quality up.
I've never done this myself because after reading about it, I decided it was more than I wanted to take on. There are lots of people around here who can advise you over on the breeding forum if you decide to go ahead. You should ask over there in any event because I might have some of the particulars wrong. It's been a while since I researched it.