NOTE: The following is based on OSX Yosemite 10.10.5. Other OS versions will have similar settings but they may not be worded the same or may be in slightly different places.
- Login to the web admin and click the Download Root Certificate button under Apps > SSL Inspector Settings. Save the root_authority.crt file.
- Open up Keychain Access by searching it on Spotlight (clicking the Magnifying glass located on the upper right corner).
- Select File > Import Items. Navigate to the file downloaded. Select System as "Destination Keychain".
Clicking the image above will load it, full-size, in a new window.
- Enter password when prompted.
- Logoff to take effect.
- On some Mac OS version you also need to do the following:
- Right click on the certificate in Keychain Access and select Get Info
- Expand the Trust section
- Under When using this certificate select Always Trust.