Write the summary. This will be totally easy, now that you've gotten all your notes in order. All you need to do is write a short paragraph covering the keys points of who? what? when? where? why? which you've already covered in your notes. Make sure that you also include the title of the story and the name of the author.
Make sure that you only focus on the main plot of the story. Don't get side tracked into Harry's Quidditch playing, or his feud with Malfoy.
Likewise, don't quote from the story itself. You don't need to replicate conversations from the story in the summary. You might need to briefly mention the key point from a conversation (like 'When Harry and his friends discover from Hagrid that the Sorcerer's Stone might no longer be safe, they go to stop the thief themselves.'