Add Admin Pages and Links

How can add an extra admin page?
I have a working php script in a file called upload.php that is in the admin directory. It's nothing special, just a basic script to upload an image to the website that can be called for creating an image link when you create a journal or page etc. The script file is in the admin folder but I've got it to upload the images to an image folder that's not in the admin folder so that's working fine.
I'm trying to put that script into a page that blends in with the admin area and has a link on the left hand menu underneath the Add Journal link or something.
A friend who will be uploading journals will want to use images in them but he wouldn't have a clue about using FTP software and I wouldn't feel comfortable giving him FTP access. His wife won't even give him the remote at home. So an Image Upload page is the safest way to go for me.

Thanks

Carl