Hi Glenys,
It is the same link as above: http://support.instructure.com/index.php?title=Overview
You will see three demo videos. The first is a good overview and about 2-3 minutes into it you will see the notifications master control page. The second one goes into that in more detail. On the third demo (just below it) you can see how assignments are graded and see the Rubrics design page. On the main Instructure page: http://www.instructure.com/ you can make a course by clicking on the big button "Try Canvas Instantly".
Definitely very cool.