How do write a SASE letter?

I am trying to send fan mail...but I need to write a "SASE" letter.
Does this mean my address has to be in the middle...or how do it work?
Please help!

Oh, and is there a minimum size the envelope must be?

Inside the letter include an extra envelope that you have addressed to yourself in the usual way, and add the postage. This way, they can send you a picture or whatever by putting it in the envelope you sent them and mailing it. Easier for them when they are responding to a lot of requests.

A "SASE" means self-addressed stampled envelope. This means you also include a blank envelope (a) addressed to yourself and (b) has the appropriate stamp along with you original letter.

So yes, you need to place your address in the middle of blank (stamped) envelope so they can send the fan letter back to you.

Good luck.