Assigning your Page to a Category
This is easy, just add this to the bottom of your article:
Where SomeCategory should be replaced by the name of the chosen category.
Please note that an article can belong to mutiple categories, this is not a problem.
After adding your page to any category, it will be automatically listed on the overview page of this category. Category overview pages can be recognized by the prefix Category: in front of the name, like this Category:Editing.