I've followed the instructions, but when I reach step 3:
Step 3: Configure
Download the DOD intermediate certificates from https://militarycac.com/maccerts/MacAllCerts.p7b, then open the MacAllCerts.p7b file.
The Add Certificates window appears.
In the Keychain dropdown menu, select System if you have admin privileges, or login if you do not have admin privileges, then click Add.
The "Add Certificates Window" does not appear. I've tried the last step selecting system, but it looks like its for modfying keychain rater than adding a certificate.