I can answer this, although you have probably discovered by now. Find the publication you want to submit to and read their submission guidelines really carefully. . It usually involves leaving your Medium tag in the response column so they can add you as a writer. You can't submit to any publication until you have been added. Then when you come to publish your article, you click on the 3 dots and then "submit to publication". Any publications you have been added to will come up there.

You will, however, need to learn how to add photos at the top of your posts and get to grips with Alt-Text etc. Most publication's submission guidelines will talk you through those things. And there are REAMS of articles on How To Do (Anything) on Medium.

Medium is a great site for practising your writing, and you will improve. I wish you all the best, A.