For your Ghost site you can add more than one staff member to manage your site. Depending on the role you can restrict capability of your staff. A staff can assign to one of the following role.
There is no limit to the number of staff in a single Ghost site.
To add a staff to your website, at first you have to invite him/her via email.
Go to "Staff" page within your dashboard and then click on invite people a modal will be open. In that modal add the email address whom you want to invite and select the role. Then Invite.
The person you have invited, will find receive an email with a link. If she/he visit that link he will be register herself/himself as an staff member to your site by generating a password.
Suspend or delete a staff user
Go to "Staff" page within your dashboard. After that select an user it will show all details of that user.
In that page on the top right corner you will see a settings(gear) icon. Click on that Icon and you will find two option "Delete user" and "Suspend user".