To put a page or file into an existing category just put [[Category:CATEGORY NAME]] at the bottom of the page or file.
If an image or media file needs to be put in a new category, then you will have to create that category.
1. To do so, put the new category name at the bottom of the file while in edit mode:
- [[Category:NEW CATEGORY NAME]]
2. Then click the "save page" button. There will now be a red link at the bottom of the file.
3.Click on the red link. This will open an edit window.
4. Add the category link for an existing category:
- [[Category:CATEGORY NAME]]
5. Save the page. You have created a new category.
You can create as many categories or subcategories, as are needed to correctly categorize the image, media file, or page.