Every day there are courses offered for writers. There are online courses and there are writing coaches who will help you walk through the steps of writing. (I know of several if you would like me to refer you).
Do you have to take a course or have a degree to be a writer? No.
Just get writing and see where the path leads you. I started writing in a creative writing course in high school. Do what suits your personality and skill level. Look up help online to improve your grammar.
If you feel taking a course will help, sign up. If a writing group is of interest, join one.
Grow it at your own pace. You should know when you're ready to take the next step of publishing a blog, writing a query letter, sending an article to a content site editor, signing up for personalized coaching, or sending a manuscript to an agent.
The point is, there is no set path for a writer. No degree is required.
The field of writing can be tough on you, though. You will have editors rip your work apart. You will want to be as prepared and knowledgable as you can be.
As you develop your craft, you will likely see yourself make dumb errors and feel embarrassed when important people point them out. You will get rejections and hurt feelings.
Good writers take the pain in stride. They take what they're dished and pour it back into their writing to be used for good.
A great way to test your skills is to put a piece past an inexpensive proofreader or editor to see how you fare. Another way to test your skill level is to send an article to an article site--preferably one that uses in-house editors that will scrutinize your work and offer feedback.
I have learned a lot from the editors at Constant-Content.com where I have many articles for sale. I don't always agree with the editor. Like art, some writing is subjective. Writing for an online audience is also far different than writing more intensive materials.
Much input can be learned online and through studying style guides. If you really love writing, you will also be a reader. So the moral of this post is READ, LEARN WHERE YOU CAN, TEST THE WATERS, and JUST KEEP WRITING to perfect your craft.