OS X Certificate Installation
Using the Safari browser, click the green SSL shield icon above which will download the certificate to your downloads folder. Browse to the download, as shown in the dialog box below, and doubleclick the certificate name:
A dialog box like the one shown below appears. Click "Always Trust".
Enter your system credentials to authorize & complete the installation.
Firefox Certificate Installation
Firefox does not use the OS X System root SSL store, so if you use Firefox, please follow the directions for Firefox.