Step 1. Click this link to download the certificate: Certificate
Step 2. When prompted, click "Allow":
Step 3. Open the CPS-Internet-Bundle.pem from your downloads:
Step 4. From the popup window click the "Keychain" dropdown menu and choose "System" from the list:
Step 5. Click "Add":
Step 6. Enter your computer password to add the certificates to your MacBook. Then click "Modify Keychain":
Step 7: In Keychain Access, click "System" on the left side of the popup window:
Step 8: In the list there are three certificates that you will need to trust, shown here:
Repeat steps 9 through 12 on all three items displayed above. They will appear in alphabetical order.
Step 9: Double click the certificate you want to trust, from the popup window click the twirl down arrow next to the word "Trust":
Step 10: In the first drop-down menu, change the option from "Use System Defaults" to "Always Trust":
Step 11: Then click the "X" to close out the window:
Step 12: You will be prompted to enter your computer password, then click "Update Settings":
Step 13. Remember you need to do steps 9 through 12 for all three items, listed again here:
Step 14. Restart your computer!
You are all done!