If someone doesn't need to be an administrator or moderator for any reason, it's helpful to know how to remove an administrator. This goes as follows:
Hold your cursor over the profile icon at the top right of the screen and click on your organisation.
In the menu on the left, click 'People'.
Click on "Edit" next to the name of the administrator or moderator.
Click 'Demote to member' if you want to make the administrator or moderator a normal member and click 'Demote to moderator' if you want to make an administrator a moderator.
More information regarding the differences between moderators and administrators can be found here