How do I begin to start a career as a writer?

I'm seriously thinking about becoming a writer. I do not know how I came up with this but I'm feeling it...seriously. However, I'm very rusty on the grammar. It's been years, you know. Should I start by taking a grammar refresher course, or dive right into taking a creative writing course? What? Please help. How to I begin...where? There are so many things I need to say. I'm starting to believe very strongly that writing is the ideal vehicle to convey what thoughts and ideas are going on in my madcap brain. Thank you