To tag someone within a post, just type their user ID. Mine is @MomzillaNC. Medium's formatter will give you a pop-up and you can choose me from it. It will propagate my name as a link.

Are you on Facebook? If so, I encourage you to join our group, WE PAW Bloggers. It's a writers forum for which I am the admin. I also manage the group-only pub of the same name here on Medium. And, I publish the group ezine on my profile.