Following are instructions on how to import client SSL certificates ("cert" or "certs") on various browsers.
In the examples we use a client cert file named 'joe-at-dummy.org.p12'. The extension '.p12' is a common one because the certificate's format is known as 'pkcs12' or 'PKCS#12'.
Note that after importing a certificate successfully, you may have to reload a secure page to get the new SSL certificate to operate with the site. You also may need to exit and restart your browser.
Note also that the instructions assume the cert file is downloaded and available on your local hard drive.