Thank you! :)
To organize your blog with tags, you can create pages. Say you want to create a page called “Poems About Cats," and you want all your poems that are written about cats to be placed under that page.
So first you create the cat page; you can figure out how to do that here. The url to that page should be something like “myurl.tumblr.com/tagged/poemsaboutcats."
Once you’ve created the page, you can start placing your poems into it by tagging them as “poemsaboutcats," and they will be automatically added to that page.
Good luck! :)