Visible name author post

Hi,
I have a website with a part, only accessible to logged-in users. They can write a post, in their role of Author. When they wrote a post, their names don’t show up with it, so you cannot see who the author was. How can I make the author visible?
(Sorry but I can not link the page because it is only visible for logged in visitors).
Thanks,
Frans van Lent

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