The System Settings page can only be accessed by Superadmin users. You can find it if you hover over the torso icon on the top right-hand corner and choose 'System Settings' like so:
On the System Settings page you will find all the other settings as well specific to scheduling, people, clients and more. You will also be able to set the notifications for specific actions as well as grant permissions for different roles.
Read more about what you can do on the System Settings: