There are no classes or degrees necessary to become a published author! You could have your work published right now, although your parents will have to participate in the process and sign contracts for you. Studying literature and writing can be helpful for some people, but it is something you can do on your own.
For short stories and poems and articles, let me start by saying that I can't give you specifics, because I don't know what genres your stories and articles are in or what subjects they cover! You will want to research journals and magazines that publish in the same genre as your story-- really look for things that print similar works. Each publisher will also have their own length guidelines-- some publications can support much longer pieces than others, so look for one that matches this as well!
You do not need to copyright your work before you begin submitting it to journals. In fact, it is looked upon as the mark of an amatuer by many editors, agents, and publishers. They will submit the paperwork when they accept your story. No legitimate companies will steal your ideas. Ideas are a dime a dozen, and they have all been done before-- the key is to take on the idea with a fresh voice!
To begin your research, take a look at the current edition of the book "Writer's Market". It is a fairly comprehensive listing of locations to submit work. Then, head down to your local public library and see if you can track down copies. Make sure it is appropriate or it will be a waste of time and postage to submit.
Each publisher has different submission guidelines, so make sure to research the specifics. Oftentimes, they are now on the web so it's much easier. Most only want you to submit one story in each submission package, and they generally have length guidelines as well.
Do not submit your story to multiple publications simultaneously unless you specify it in your cover letter and you are sure that the particular publishers accept simultaneous submissions.
For formatting your story and manuscript, see if you can locate a copy of "Formatting & Submitting Your Manuscript" (which is actually published by the folks at Writer's Market). It's my favorite reference for all sorts of literary queries. I write poetry primarily, but my submission package generally includes a cover letter introducing myself and the work that I have enclosed, plus my poems (each page having my name, address, and the page number at the top). Like "Writer's Market", many public libraries have this book in their reference section!
It could take a long time, and be prepared for multiple rejections. Such is the life of an author! But, if you are persistant, you will find a home for your story.
Let me also suggest checking out the website http://www.anotherealm.com/prededitors/ to help you avoid other scams in every aspect of writing. It isn't the absolute authority, but it can be very helpful for research.
If you do complete a book-length manuscript (generally 60,000 to 90,000 words for adult fiction, less for children's books), then you have a whole other set of places to research from. You must have a completed manuscript before you begin shopping it. I highly suggest looking for a literary agent first, because they are a valuable ally in getting your book into publisher's hands and negotiating your contract and rights.
Here are six websites that can help. Read them thoroughly (especially Miss Snark-- love her!) and research, research, research! These can help you determine if the agent is legit or not:
http://misssnark.blogspot.com/
http://www.agentquery.com/
http://www.anotherealm.com/prededitors/
http://www.publishersmarketplace.com
http://www.duotrope.com
http://www.sfwa.org/beware/twentyworst.html
In the meantime, I would recommend reading as many books as possible in the genres that you like to write, as well as about the craft of writing. When you are reading other fiction books, pay attention to how the authors structure their work.
Here are some of my favorites about writing:
1) "Writing Down The Bones" by Natalie Goldberg
2) "Bird by Bird" by Anne Lamott
3) "On Writing Well" by William Zinsser
4) "How to Write Science Fiction & Fantasy" by Orson Scott Card
5) "On Writing" by Stephen King
6) "No Plot? No Problem!" by Chris Baty
7) "Eats, Shoots, and Leaves" by Lynne Truss
8) "The Elements of Style" by Strunk and White
Also, take a look at a few websites where authors gather. Some of them have very helpful articles and forums. Holly Lisle has a fantastic website that has articles on both the business and writing aspects:
http://hollylisle.com/fm/
Forward Motion is a wonderful, helpful community:
http://www.fmwriters.com/
Absolute Write is one of my favorite author communities, with a vast pool of resources and helpful people:
http://www.absolutewrite.com
Write every single day. Set a target for yourself. For instance, my goal right now is to write 1,000 words a day. I get this done before I go on the internet, read, watch TV, or goof around. To begin, maybe set an easier goal for yourself-- try 250 words each day. Write in a journal as well, if you feel so inclined!
When you get ideas, find a way to record them as well. I have a spiral notebook that I keep just for that purpose. This way, when I want to begin a new project I can read through my notes and find just the right idea!
Also, never forget how important it is to edit and rewrite! When you finish a short story or novel, I suggest setting it aside for a month. Don't look at it or think about it (if you can help it). Work on another project. Once that time has passed, go back and read what you wrote. Try to be objective-- are there parts that need to be expanded? Cut out? Rewritten? How is the grammar and spelling? Editing could (and should) take more time than the original draft!
Good luck, and keep writing!