There are four roles that you can assign to people who you want to blog with: Administrator, Editor, Author, and Contributor.
Important: Please be careful of the roles you give users on your site. If you add a user as an administrator, you are granting them full access. This means that she/he will be able to delete pages, posts, plugins, themes, etc…
Here is the process of adding a new user:
First, hover the Users tab in the WordPress dashboard
Click on Add New
Enter Username and Email
Click on Show Password
You can modify the password here if you want. Keep in mind a strong password is preferable.
Choose the role (See below for the rights of the different roles)
Click on Add New User

Select the right role you want between these four:
Administrator
An administrator has complete control of your website and can do absolutely everything. This person has control over posts/pages, comments, settings, themes, plugins, import, users – everything. Nothing is off-limits, including deleting everything.
Editor
An editor can view, edit, publish, and delete any posts/pages, moderate comments, manage categories, manage tags, manage links, and upload files/images.
Author
An author can edit, publish, and delete their posts, as well as upload files/images.
Contributor
A contributor can edit their posts but cannot publish them. When a contributor creates a post, it will need to be submitted to an administrator for review. Once a contributor’s post is approved by an administrator and published, however, it may no longer be edited by the contributor. A contributor does not have the ability to upload files/images.