In order to use the sprinkler, you have to dig with the shovel in the farmland from where the water is to where you want the sprinkler to be. After you have a path dug to where you want to put the sprinkler, you just select it and throw it into the water. Once you have it in place, I'd reccomend throwing rocks or lumber into the water path you created to make it disappear and tilling the land to maxmize places to plant seeds.