You put the weaker one in the container. If you put the stronger one in the container it just ****es her off and when you eventually let her out she goes on a scorched earth policy around the tank.
Put the smaller one in the container and put the container RIGHT in the anemone, or right next to her favorite lair. She won't like it one bit, and may initially attack the jar. Eventually she gets tired of attacking it and will just accept it being there. Meanwhile the little guy in the jar will initially be scared to death, but once he realizes he isn't about to die he will perk up. Usually he will start to display submissive dances and act in a more normal fashion. Wait until the female shows no interest in him other than to come look at him every now and then. Wait at least a week - 10 days until she gets totally comfortable with the new situation, and the little guy has had the chance to recover and get stronger. If you need to feed the little guy squirt a LITTLE food into the jar with a baster.
When you eventually let the guy out, you may want to do it at night so he can settle into the nem without her knowing what is going on. Every clown is different so let her behavior be the guide of what you do. Sometimes with a really nasty female I put a small mirror in the tank. She is so upset at her reflection it often distracts her from the male for a bit...