The Extra Theme’s post layout includes an “About the Author” box to display a bio about the post’s author. If you’d like to remove this, you can now do this from within Extra’s theme options menu. From your WordPress dashboard, go to “Extra > Theme Options > Layout > Single Post Layout”. Here you’ll find a “Show Author Box” option, like so:

Change the Setting to “Disable” and click “Save Changes” to get rid of the author box from your posts.