John,
The username and password, you're going to be getting from your Reltio admin. If you are the first person on the ground with Reltio, you get that information basically when your project starts for your Reltio implementation, the main point of contact will get a document with their login and they'll be the admin who can then give access to other folks. From that point, you might connect it to your SSO and then authorization will come through your SSO.
Check out the show on Getting Started with Rest API's and Reltio below.
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Joel Snipes
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