I hate this question. Because, when you have a WordPress website, you already have a blog. So it leads me to ask in reply, "What do you mean by the word "blog?"
"Well, er... you know, a blog!" they say.
Here's the deal:
WordPress is blogging software. So you already have a blog. Post articles. Turn on comments, or not. It's up to you.
Now if you mean by "blog" can you post drivel about what you ate for breakfast... the answer is NO!
You are required to post short, interesting articles. Or the blog police will show up at your door and throw up in your face. Just kidding, but, please... put up interesting stories and ideas.
Your website represents you. Have it represent you well.