Just add the page name of the category to the bottom of the page. Do not edit the category page.
The marvellous thing about Wiki is that not only can you see all the things that this page links to, you can see all the pages that link to the page you're on as well using the BackLinks function. By invoking the BackLinks plugin you can have the BackLinks listed right inside the category page itself.
Categories should be neither too specific nor too broad; there's little value in having categories with three items in them, but there's also hardly a point to a category that lists half the universe's topics.
The ramification of the previous paragraph is that in pages not belonging to a category, you must not link to that category page by using its name. Instead of writing !CategoryFoo? you have to write !Category:Foo - note the extra colon. This creates a link to that category page without putting the linking page in its BackLinks. A corollary is that pages which link to a category page but do not belong to the category will not and cannot be backlinked from the category page.
Don't know where to start? You might like to browse pages on a particular topic. The following are all categories that exist within this WikiWikiWeb: