Canvas is a web-based learning management system used by Oregon State University and many other institutions of higher education. Educators (Professors, Instructors, GTAs) and students use Canvas to access and manage course materials online. There are a variety of features on Canvas that might be useful to you in your time as a GTA.
Oregon State's Canvas subscription and use is through the University Information and Technology via Learn@OregonState, which is the university service for learning technologies. There are several resources available for using Canvas and helpful Instructor (Faculty and GTA) tools.
It may also be helpful to work through some of the modules in the Oregon State Canvas Academy, which lays the groundwork for using Canvas through the Canvas interface.
To ask for assistance, please email Canvas@oregonstate.edu.
There is also 24/7 Canvas support. For help, select "Contact Us" on the main Canvas assistance page, or call the Canvas support hotline at 1-844-329-3084.