I keep placing a villager on and around the lagoon, is there a special one ore a special spot to set him/her so they get the idea to use the water?

i tried .. they stubborn

See this regarding help for the Virtual Villagers puzzles: help info

Been there.

Try reverse "psychology" If they won't use the water from the lagoon, try motivating them by having them looking at the field.

BINGO! Now if I can just keep them working. How long till it works?

If they are set to the right job, they do till done, if not, they do only once.