WordPress not recognising my custom theme

Solution:

How your directory structure should look like:

wp-content
    themes
        your-theme
            index.php
            style.css

Your CSS header looks fine, does your theme also has a index.php file? If not then you should add one this is required.

Adding Template: appth.at is not required, this is only needed when your creating a child theme, if you are then you should note the folder of the parent theme there. ie if you’re creating a child theme for Twenty Eleven then you write: Template: twentyeleven