If I were you, I would write why you are a fan of the person, and describe what you like about them. If it is an actor/actress say your favorite movie/show/play they were in, your favorite role of theirs, favorite scene, etc. etc. I would pretty much make it like a regular LOR but instead at the end of requesting the autograph, include your Name and Address.

Hope this helps!
Cody

So I do have an email to send to a manager and I don't really know what to write in the email. I really want to request an autograph but should I just say that or should I write more?