To promote medium membership you need to click again on your profile picture, scroll down to settings again, again scroll one over to Publishing. Scroll down until you see "Promote Medium Membership". Click on "share your membership referral page" - copy the link, go back to your article and open a new paragraph that brings up the + button; click on the embed feature and embed the link. If you don't' know how to embed or this doesn't make sense, get back to me and tell me where you get stuck and I'll try and break it down more. A🙏