Hi there!
We're happy that you're enjoying the game!
Healing is a skill just like any other in the game and it needs to be practiced. In the early stages it can be difficult to train a villager as a healer but don’t give up!
Drag and drop a villager onto a sick villager until they start to learn how to heal other villagers. If you don’t teach your villager how to become a healer, they will not be of any help to your village.
In a puzzle in Chapter 2, there is a building you'll create that will help train your villagers to become much better healers.
Let us know if you have any other questions and thanks for playing!