Go to https://powernotes.com and click Login in the upper right corner.
Click Sign Up on the login page.
Sign up using your school provided email address. Example: jdoe1@saybrook.edu
Add the browser extension by going back to https://powernotes.com and click on Resources and Install Extension.
And in the extension, use the Enable PowerNotes toggle to turn it on when you need it (Yes) and turn it off when you don't (No)!