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The URL can be pointed at any properly configured instance of the IHTSDO CIS. The username and password are authentication credentials for that service.
Administration of CIS
Note: in order for CIS to work properly, it has to be configured with the namespaces that you intend for your users to make use of. This is generally fine for the international edition, but for UAT or DEV environments, it may require more maintenance. This will require having an account that authorizes you to log in and make changes on the admin console, e.g. https://cis.ihtsdotools.org/admin/pages/login.html