Adding an OER to Canvas, or distributing it to your class in some other way, is very simple.
The most straightforward way is to simply provide a link to the textbook's page, like this:
In this class, we will be using Anatomy and Physiology by Betts, et al.. It is a free textbook available from OpenStax here: Anatomy and Physiology on OpenStax
Many OER providers also have Canvas integration for their materials. OpenStax, for instance, invites faculty to register when they adopt a textbook, which unlocks many instructor features, including Canvas "cartridges" which can be loaded into your course.
Source: Christian Brothers University Plough Library. Open Educational Resources : Integration with Canvas. Retrieved from https://libguides.cbu.edu/oer/canvas.
Canvas Commons is a learning object repository where you can find, import, and share resources. You can share learning resources with other users as well as import learning resources into a Canvas course. The video below shows an example of how to import an OpenStax course from Canvas Commons.