Canvas is made by a company called Instructure. They have produced quite a few training resources: videos, documentation, and PDF handouts about Canvas. These are generally great resources, if a bit verbose. If you have time to sit down and go through some of these instructions, it will be helpful.
If you're looking for a quick answer to a specific question, try doing a Google search.Canvas is used by hundreds of institutions, so there are lots of online instructions. Try putting the word "Canvas" at the beginning of your search. Or, to search the official documentation, add "site:canvaslms.com"
Example Google Search: Canvas extra credit
Example Google Search: site:canvaslms.com setting up peer review
Canvas Guides - Official Documentation
Canvas Guides Home Page - Start here
Canvas Video Guides - videos for students and faculty
See the subpages listed below for some extra documentation resources for using Canvas, written at Biola.