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.
Note that Canvas recommends you do this first on your Test/Beta site, get it working correctly there, and only then configure it on your Production site. But be aware thta every couple of weeks Instructure repalces your Test/Beta site config with your Production config, so you might have to repeat configuring the below multiple times if it takes you too long to complete your testing.
This document tells you how to navigate to the page that has the SAM config options on it:
https://community.canvaslms.com/docs/DOC-4284
But the basic thing is to click on "Authentication" in the left-hand pane of this screen:
And then click on SAML in the right-hand side of the subsequent screen: 