From b2evolution manual

This manual page is outdated. NEW PAGE: Setup A New Blog in b2evolution v5+.

Here are some simple steps to add a new blog to your site:

1. In the backoffice under the Blogs tab click the link at the bottom to create a New blog.
2. Fill out the form for creating a new blog.
3. Click Save.
4. Now the blog is created and administrators have permission to post to it. If you want other users to be able to post to the new blog, then edit the blog and go to the permissions sub tab to set the permissions as you need them.