I have one of these. They're very unweildy! I got rid of mine last year because it made such a mess with the little seeds it produces. It will produce a bloom too, which it looks like yours already has some.
Since these are so big and messy, I just keep planting the seeds and get rid of the plant when it gets too big. I'd cut off what you want to divide and water into dirt. Give it time to root and you should be in business.