To add people, users and administrators. All this is done through the posts section on the left side in the admin bar. If you click posts you notice a People tab.
To add your staff or make a team row on a page. Add people here and then you will be able to tag them on posts that are written or featuring on a staff page.
If you are looking to create users than can actually edit the site than that is done on the Users table. If you want the user to manage the website set them as an Administrator. If you want the write content but not have access to the important parts set them as an Author. If you don’t want them to have any access to managing the website set them as a subscriber.