Hello and welcome to the world of writers!
While I agree with everyone, I'm also a risk taker. I believe that whether you post or not should be based on your confidence. Ask yourself:
-Do I like what I have written?
-How far will I take this story?
-Will I get stuck any time soon?
-What tools do I have to use and improve every day?
There's a first time for everything, and the only way you become a better writer is by writing, reading, and seeking advice/reviews.
Everyone has the potential to be a writer.
I think this has turned to a pep talk so let me get to the gist of things. If you want to post your story and believe other's will enjoy it then go ahead. If you don't succeed the first time and don't get many reads or likes, it's okay. Keep improving your work. Writing is a lifelong journey. And even if it's one person, it's an amazing feeling to have someone comment and love your work.
Some tips:
-YES, use things other than Word (I use Word, Grammarly, Google docs, my beta, and reread even then). Other sites can catch things such as sentence fragments, overused words, mispunctuation, and passive voice. I am using Grammarly to type this right now and editing as I go. (I have a sentence fragment I don't know how to fix actually lol).
-Ask friends or others to read your work.
-Read your story out loud to check your flow.
-Never ever give up.
-Enjoy it. When you write you are creating your own private world, anything goes. Don't let other's restrict your creativity and just have fun with it.