Not sure if this will help, but here's a link that explains how to do it with one of two different ways:
Also, in some themes (I don't know about the one you're using), on a post and page, when you are in the back office, on the top right is a tab 'screen options'. It's a drop down. In there you can uncheck author, date and more. Some themes do not have that option.
Another way is in 'customize' there should be a tab that says "Post Information" in that tab, there should be one for "Meta Information". In there you can uncheck or check the things you want displayed.
If you're goal is to hide your user name, you can do that in "Edit my profile". I never show my user/login name. I have a default name (my company name) that I set it at. I would do this step no matter what. It helps to keep the shitheads from hacking your site.
Hope that helped!!!