How do I - in my Firefox Private browser, "clear cookies/cache for facebook.com (and fb.com)"?

      Suspicious page blocked for your protection
      https://www.faccebook.com/

     Your connection to this web page is not safe due to an unmatching security certificate.

I can't bring in www.facebook.com so I can "sign-in" to my FaceBook account.. When I enter "www.facebook.com " into the URL, my virus program (BitDefender) produces the following message on the monitor for me: Suspicious page blocked for your protection https://www.faccebook.com/ Your connection to this web page is not safe due to an unmatching security certificate. This means that the certificate was issued for a different web address than the one it is being used for, and you run the risk of exposing your data by accessing this page.