Rhubarb is easily divided - probaby best done in spring or early fall, but if you have a large plant you could divide now and keep the transplanted tubers well watered. I would just leave the parent plant in the ground and spade out a side tuber. The new plant probably won't give you too much production this year, but next year it should do great.

Some people grow it from seed but that is more difficult.

Also, to improve yield you can prune off the central flowering stalk when you see that coming up.
Rachel