SEO is constantly changing with each update from Google, but I can give you a few general guidelines.

I know it sounds generic, but the main key is to write quality and helpful content for your audience. You can target a few keywords in your niche if you are looking to rank for them. You want to add them naturally, and not make it look awkward.

Medium has a high domain authority, which makes it easier to eventually rank your articles. It also seems that longer articles tend to rank better than shorter ones, but that's just my experience.

Anyway, that's just from my perspective as a writer. Some people specialize in marketing and they know much more about it than I do.