You need credentials to follow the tutorial, which you only receive after Canva approves you as a Print Partner.
Step 3: Get a deeper understanding
The tutorial is an excellent starting point, but it doesn't cover all of the capabilities available to Print Partners. Once you've developed a basic integration, dive into the rest of the documentation:
Concepts - Overviews of the components that make up an integration.
How-to guides - Short, recipe-style guides for customizing an integration.
Troubleshooting - Quick solutions to common problems.
REST API - Reference documentation for the REST API.