Each college using Canvas has one or two people who have been established as "Canvas Administrators" for that college. The person(s) in that role have access to their Canvas site with "administrative privileges", including being able to configure how authentication is done for their Canvas site. That is the person who has access to "turn on" SAML authentication for the college site, and fill in the needed info for that to work.
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But the basic thing is to click on "Authentication" in the left-hand pane of this screen:
And
And then click on SAML in the right-hand side of the subsequent screen: 
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There is a dropdown with multiple choices, You want to choose 'eduPersonPrincipalName'. That has to match what you fill into the LOGIN_ID in the Canvas provisioning feed.
* Identifier Format: urn:oasis:names:tc:SAML:2.0:nameid-format:transient
(choose the above value from the drop-down and Save your changes. The drop-down should have the following set of choices:
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