If you have a Chess.com account, you already have a Chess.com blog—no need to create one!
To find your blog, hover over 'Social' on the left-side menu of any Chess.com page and select 'Blogs'
From the right-sided menu, you can click on 'My Blog' to see all your blog posts or 'Create Post' to create a new one:
Check out this article to learn how to change your Blog's URL and Title: How can I change my blog's title and URL?