Adding ‘Written By’ to Author Box

I just want to make a small change to my author box (I recently just changed my theme).

It just has my name, Whitney S. (you can see it when you click on an individual post on my site).

I really want it to say, ‘Written By Whitney S,’ but I don’t know how to get the ‘Written By’ to be visible (an example of my previous one – https://i.imgur.com/spjXdvH.png).

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