I've done a lot of my learning with the Canvas API based on trial and error. You begin to understand how to write the calls, then you get a better feel of what you can accomplish (and how complicated you want to make it). I've run API calls in 3 environments: Using Postman (you can download the tool for free), using the Canvas LIVE API site https://yourinstance.instructure.com/doc/api/live (you can use this for test, beta, or live), and using PowerShell with the Invoke-RestMethod cmdlet. I know Python can be used as well, but I haven't worked with it much personally. For any of these methods, you'll need to generate an access token in Canvas from your account settings.
It's easiest to start with single API calls-- when you want to return a piece of information about a single endpoint. Ex- return information about a single course. The Canvas LIVE API gives you an easy way to run these calls and see how they are structured using the "Try it" feature. This will run the call and make any changes if it is a POST, PUT, or DELETE call, so use with caution.
You then can try exploring using a file to run API calls on a list of variables. Ex- return information about each course in a certain subaccount. You'll need to move to another tool such as Postman or PowerShell to accomplish this.
The most complicated would be taking information returned from API call and feeding it into another call, which is the basis of what you'd want to do above.
The general outline of what you need to do is listed below. Use the API documentation find your correct calls, then figure out what tool you feel comfortable using to string these calls together. You will need to use a tool/coding language to accomplish some version of a foreach loop and write to an external file.
1) GET a new quiz (Either by using the quiz ID or finding a list of quiz IDs for a course using a Course ID)
2)GET a list of submissions using the quiz ID(s) from step 1.
3) Foreach submission returned, take the user ID and pass it to a GET user info call
4) Foreach user info call, take the email address and write it to a file.
I hope this helps give you a little more direction.