Only One User

At the moment only the owner of the site has a federated username [email protected] and this is the only one that will post to federated site when they post

I want to have more users or all my users to have a [email protected] for federation because I have a person on the site that writes our blog posts, and even if they can’t have there own username but have the main username show the posts when they post

is this possible and if so how do I set it up please

The page I need help with: [log in to see the link]