To install the CERN Certification Authority certificates in the keychain:

1. Download the CERN Root Certification Authority 2 certificate(s):
   • CERN Root Certification Authority 2 Certificate
2. Open each downloaded file and double click on it
3. When you are asked to trust certificates signed by the CERN Root CA, click "Always Trust"
4. Provide administrator credentials to allow the operation
5. Download the CERN Grid Certification Authority certificate(s):
   • CERN Grid Certification Authority (1) Certificate
6. Open each downloaded file and double click on it
7. Since the root certification authority is now trusted, the certificate should automatically be installed in the keychain

The above procedure should by default install the certificates in the login keychain. If you want the certificates to be stored in the system keychain, you can move them from the Keychain Access application.