Twenty Twelve comes with some page templates: Front Page & Full Width. These are in the folder /page-templates.
I’ve created my own template and saved it into this folder, but it is not present to be selected when editing a page.
There is no mention of the two page templates in functions.php
What do I need to do to include my new page template?
Put the template file in your theme and add the following comment to the top of your file after the
WordPress will pick this up and in the page templates dropdown you will see “This is the name of your template” listed as an option
According to http://codex.wordpress.org/Pages#Creating_Your_Own_Page_Templates
what you need to place at the top of the template file is
and then the template will show up in the Template drop down in Page Attributes meta box and you’ll be able to select it.
And, you should be working with a child theme, too, in order to not lose your changes and templates when twentyeleven is updated. See http://codex.wordpress.org/Child_Themes