I would not recommend to do this. Unlike some other corals that can be fragged, anemones are one of those animals that you should wait till nature does it on its own.
I have read that you can split an anemone by cutting into it. But the survival rate for doing this method is almost slim to none.
Also, not to mention that once anemones decide to die, they can and will cause havoc in your tank. It will cloud and cause an ammonia spike so fast, that you can only hope that all of the animals in the tank make it. Believe me, I had one die and it pretty much destroyed my water :uzi: parameters in my tank. I had to do an emergency 90% water change and 50% water changes every other day for a week to lower the ammonia to zero. That's how bad it got.
Don't tempt fate. Let the anemone split on its own. This way, you get 2 very healthy animals.