Accounts are created on each site individually. However, if an account requires visibility of more than site this can easily be achieved.
Once an email address is activated on Manager 360 creating a live account, this email address can be used to create an account on each additional site without further activation. The password and set up of the account are shared between the sites.
The privileges are still maintained on a per site basis so if an account requires visibility of more features at one site than at others then this is easily achieved by adjusting the privileges of the account in each site as described in Setting Account Privileges.