This would be a good topic for a three-point essay--a paragraph of introduction, a paragraph of conclusion, and a main body with three paragraphs.
The redemption theme in the novel is developed through Amir's character and his history with his childhood friend, Hassan. A good structure for the main body paragraphs of your essay would be this one:
Main body paragraph one: Explain what happened between Amir and Hassan when they were children, the terrible incident when Amir saw Hassan being attacked by the neighborhood bullies and did nothing to even try to save him.
Main body paragraph two: Explain how Amir felt about his cowardice and his betrayal of Hassan, the guilt it caused him. Explain how Amir lied and forced Hassan to leave because Amir felt so guilty he could not stand to be around him.
Main body paragraph three: Explain how as an adult living in America, Amir returned to Afghanistan to save Hassan's son, despite the fact that doing so was very dangerous. Explain the terrible beating Amir took in saving Hassan's son.
In your conclusion, you can tie it all together by talking about Amir's redemption, how he found forgiveness for his sin of betraying Hassan by saving Hassan's son. Explain how Amir felt about himself at the end of the story, contrasted with how he felt about himself as a boy when he was too afraid to help his friend.
There are many good passages in the novel that you can quote in your various paragraphs to support your discussion. Also, the eNotes links below will take you to some excellent study guides that you will find very helpful. Good luck!
The person above me has done a great job laying out the idea of redemption in an essay format.