The easiest way of creating a new spell article is to copy one of the existing ones; I recommend Hag's Blessing. Browse to it, click 'edit this page', copy the text, browse back to the home page, create a new article (there's a box on the right), paste the text into it and modify to your heart's content.

The key elements are the infobox, which has documentation, and the template, which you can otherwise use by inserting the following text
 {{subst: spell}} 
. If you use this method, when you save the page, the contents of the template will be copied to your new article, allowing you to modify it.