At the top of the Blogs page, there should be the words "Create a new blog." This is the option to create your blog, and therefore post blog entries on it.
1. Go to the "Blogs" page.
2. Click "Create a new blog."
See? Easy. Oh yeah, and I think you need to reach muffin rank. To unlock the rank, you need at least 5 posts. Then the option would be available.
Hope this helps!