Your username is set as the blog author by default. You can either change the username or hide the blog post author.
Change your account username
You can change your username in the Account Settings.
Hide the blog post author
Open the blog post in question:
Then, click on the header section and open the header settings:
Hide the author by clicking on the eye icon.
Hide the author for all blog posts at once
To hide the author for all blog posts, find the blog page/section (click on the blog section) on your website and open its settings.
Then, go to the Style tab and hide the Author.