It is difficult to tell from your post... Are you wanting to propagate
from the above ground parts of the plant, or do you just want to
propagate and thought this was a good place to start?

For most running bamboos (especially the larger ones that carry a
substantial amount of energy in their culms), the easiest way to
propagate is with rhyzome cuttings. It is pretty simple... Just:

1) Go around the plant with a garden fork loosening the soil and
feeling for rhyzomes. You'll know when you found one as they are very
strong. Like bamboo culms running horizontally just under ground.
2) Loosen the soil under and along the rhyzome... Follow it out away
from the plant to it's end, and back toward the plant as close as you
want to go.
3) Cut it off and pull it out... You are going to break off some of the
roots, but try to do as little damage as possible.
4) Get a hose and wash off much of the dirt... This does two things. It
keeps the rhyzome wet, and it makes it easier to see the rhyzome's
nodes.
5) With sharp shears, cut it into sections... Always cut in the middle
of the internode, and make sure each piece has at least three nodes,
some roots, and one or more buds.
6) Pot them up... Put each rhyzome piece in a pot (or the ground) with
roots going down. Make sure your soil is loose so itsifts down around
the roots and doesn't leave big air pockets. The top of the rhyzome
should be just under the surface... Maybe 1 inch or even 1/2 inch deep.
7) Water it thoroughly. After an initial soak, keep it damp but not
sopping.

If the weather is good, you should see a high success rate... Depending
on the species you should get anywhere from 50% to 90% that grow.
Larger pieces of rhyzome with more roots and buds of course both
increase your chances of success, as well as increasing the rate the
plant will establish itself.

The minimum size of rhyzome I listed above is what commercial nurseries
use to get 1 gallon pots. Double the size and it might be sold as a 5
gallon.

Cheers!
Jeff