How to Add Authors to the Blog Builder
Click on "Sites" > "Blogs" > "Settings" (cog)

Click on "Author" tab located on the left side > "+ Add new author"

Add your author name, photo, image alt text, social pages, and author description > Click on "+ Create Author" once you are ready

Supported Image size for Author is 10MB.
Please Note:

Category, Keywords, Author, and Slug CANNOT be updated after the blog has been published. The developers working on a solution which will be released soon