The conclusion is found in the final chapter, after Digory heals his mother with the apple from Aslan. That chapter (titled, appropriately, "The End of This Story") moves from real-time action to summary, and that's where things are tied up. This would be roughly the last four pages of the novel, in which the doctor comes over and pronounces Digory's mother cured, they bury the rings, and we get an overview of how this story fits in with the rest of the Narnia books, especially The Lion, the Witch, and the Wardrobe.