Creating an Additional Author is Simple. It only takes a couple of steps.
1. Select “Users” from the left control panel of your WordPress Dashboard.
2. Select “Add New”
3. Create a New Username and Password (anything will do, the Name here is what the posts from us will show up as). For security reasons, make this different than your normal WP admin username and log in. Something you have never or will never use.
4. Set the Role as “Author” then click “Add New User”
You’re done. Now complete the form, providing the same username/password you just created.