you have to have a villager that has "healing" as a skill level. drag one of your villagers to the 5 various plants, and keep doing so until it says your villager has improved at healing. when they have some healing, then drag that doctor to the sick person...they will heal them. for any other information, go to the top of page to "forum list", then scroll down to the bottom of that page to "VV2 - the lost children GUIDE. It will give you various hints there on the game itself.