Check out the Codex page about creating your own page templates.
The files defining each Page Template are found in your Themes directory under /wp-content. To create a new Custom Page Template for a Page you must create a file using a plain text editor (e.g Notepad or TextWrangler).
Basically, create a php file, and put the following code in it:
<?php
/*
Template Name: Snarfer
*/
?>
The above code is required and defines the snarfer.php file as the “Snarfer” Template. “Snarfer” may be replaced with most any text to change the name of the Page Template. The Template Name will appear in the WordPress Theme Editor for editing. For more information on Theme naming conventions see reserved Theme filenames for file names you should not use.
By your request
A tutorial for adding fields to an existing options page.
Hope it will get you trough.