It's easier when you know what you gonna write about if you have a niche. But I began without a niche. All I knew was I love to write. From my experience in one of the Middle East countries to job hunting to discovering personalities or psychology terms of what people go through in life... I don't know what niche to write. Somehow watching movies became another form of topic for me like what gems I found in those movies... Mama Universe can always tell me something from movies too.
To answer your question... Where do you begin? Begin where you are.
You'll never be ready if you keep waiting till you're ready. To have created an account here means you're ready to begin already.