If you can catch the clownfish, put the nem and the clownfish in a small tupperware container (or similar) with holes for circulation so that the fish have no where to go but into the host. Once they have experienced the pleasures of getting stung and growing their slime coats for protection they will search for the anemone because that is where they feel at home.
If you can't catch the fish and anemone, then stop feeding the tank for a couple of days and let everyone get hungry. (If the fishes start eating each each other, discontinue this method immediately.) Then careful target feed a few pellets into the anemone. With any luck the fish will swim in to get to the food. Repeat until they move in for good.
Otherwise you can use a net or a hand to "chase" the clownfishes around the tank. Keep chasing until they dive into the nem for safety. Once they are in, keep lurking for awhile and threaten them every time they start to leave home. They'll catch on. (This method works really great if the nem is in a cornor of the tank, and you can chase them towards the corner.) Hybrid method of feeding a few pellets and chasing can also lead to positive results.
The floating container with circulation holes is the easiest for obvious reasons. Once the fish swim in, and stay, then carefully open/sink the container and put it in the tank where you hope the anemone will stay. IF you can put a rock in the container to sink it, or wedge it safely the nem can then crawl out and find where it wants to be.
