The blog can be used for whatever you want. We encourage you to post about writing, but you can also post your work for display (rather than critique in the workshop), or post about your personal life or generally anything you'd like.
After you've clicked the Create Entry button, you'll be taken to a form to enter your blog information. It looks like this:
Enter your blog title, blog post, entry date, category (you can create new ones) and set your privacy settings. Then click the "Create" button on the bottom.
You've just posted a blog.