If Firefox displays a message "To protect your computer, Firefox prevented this site... from installing software on your computer.", press the button labeled "Edit Options..." and click "Allow" add libx.org to the list of websites from which extensions may be installed. Then click "Ok" and visit the "Install" link again.
In Google Scholar you can customize your preferences so it knows you are using the Claremont Colleges Library. This will help you link to library resources such as subscription-based journal articles when searching, whether you are on or off campus.