AuthoredIn is in beta, and you can use it for free right now.
To get started, install the AuthoredIn Extension from the Chrome Web Store:
After you have the extension installed, log in to your LinkedIn account and go to the home page. You will see the AuthoredIn logo in the feed, next to "Start a post" button. If you don't see it, try reloading the page.
Then proceed with the onboarding steps outlined here.