It sends out runners underground -
and it runs and runs and runs ....
Starting a new plant is as easy as digging up a smallish one,
being sure to get deep enough to get some nice roots,
then replant it in a pot, or directly into the ground (that is, if you're sure you don't mind it trying to take the place over -
at my house, we call it a "garden hussy"
because of the way it spreads itself around -
it sprouts up as much as 10 feet away from the mother plant ). **
Be sure to keep it well-watered until it is established.
It can also be started from semi-hardwood cuttings -
so if the piece you got was 6 or 8 inches long,
it might very well work. Just remove all but a few small leaves
near the tip, and any flowers
It might root in water,
but I use the Forsythe pot method for nearly all my cuttings.