For detailed instructions, see the following Instructure guides:
Note: files uploaded to ungraded Discussions count against a user's
personal file storage limit, while files uploaded to graded Discussions to not. If the Discussion is ungraded and the files are large, we recommend that users upload the files to their campus OneDrive account (below) instead of loading the files directly into Canvas.
Uploading to your campus OneDrive account
Users may want to insert files into Canvas Discussions without the files counting against their
personal file storage limit (above). In those cases, we recommend that users upload files to their campus OneDrive account and use the Office 365 integration to link to the files from there:
Note: This method will attach the desired file to the discussion post, but it will not embed images directly in the body of replies. If the user wants to display an image directly in their reply, we suggest uploading the file to Canvas (above) instead.