We used moss that was growing on the side of our house and simply peeled it off the wall a put it where we wanted it, making sure that some of it was touching water. For moss patches that weren't touching water, we placed a clean candlewick under the moss, and the other end of the wick into the pond. The moss took pretty quick and expanded significantly . . .

. . . until we had a algae bloom and put the algae killer chemical into the water - that majorly damaged the moss . . . duh, we should've figured that would have happened, but too late now . . . Luckily, we still have a good patch or two growing.