You can use the Content Selector to insert and upload course images into the Rich Content Editor. The Rich Content Editor is used in features that support the editor (Announcements, Assignments, Discussions, Pages, Quizzes, or Syllabus).
Open the Rich Content Editor using one of the Canvas features which support the Editor.
Locate Content Selector
The Content Selector will automatically open when the Rich Content Editor is opened.
Open Images Tab
Click the Images tab.
You have the option to link to existing course images , search the Flickr Creative Commons site  or upload a new image .
Click the Upload a new image link to add a new image to the course.
Upload New File
If you choose to upload a new file, select a folder for the file . Click the Choose File or Browse button .
Note: If your institution requires setting a usage right for files, you can still upload a new image, but you will have to set the usage right in the course Files page.
Click the title of the file you want to insert . Click Open to upload the file .
Insert Alt Text
To add alt text to your image, insert text in Alternative text .To add the image as decorative, click the Decorative image box . If the Decorative Image checkbox is selected, the alternative text field is grayed out.
Click the Upload button. The image will be automatically inserted into the Rich Content Editor when it is has been uploaded.
Note: If the size of your file exceeds your course storage quota, Canvas displays an upload error. Talk to your system administrator or choose a different file to upload.
Click the Save button to save any changes to the post made in the Rich Content Editor.
Note: When using the Rich Content Editor in Assignments, Discussions, Pages, and Quizzes, you have the option to Save & Publish. When using the Rich Content Editor in the Syllabus and Discussions pages, the Save button may appear as “Update Syllabus” or “Post Reply”.