How does Atticus use Mrs. Dubose's death to teach the children about courage?

This lesson in courage has to do with what Atticus wants his children to understand as courage's true definition. Jem and Scout view their father as courageous. This realization came when they saw him shoot the mad dog, but he wants them to see the word from a different perspecrive, and he uses Mrs. Dubose's death as a lesson.

Atticus defines courage as “…when you know you are licked before you begin but you begin anyway and see it through no matter what.” This refers to the fact that he sees Mrs. Dubose overcome her morphine addiction before her death. She was determined to beat it no matter the cost, and the cost would have been to die in great pain. That she faced this pain in order to overcome is how Atticus defined courage to his children.