To install an SSL certificate on your Mac running macOS Yosemite or El Capitan, follow these organized steps:

1. Obtain Necessary Files:

   • Retrieve the .crt (certificate) and .ca-bundle (intermediate certificates) files from your Certificate Authority.

2. Open Keychain Access:

   • Launch the Keychain application on your Mac.

3. Import Intermediate Certificates:

   • Drag the .ca-bundle file into the Keychain window to add intermediate certificates.
   • Verify by searching for "Comodo" in Keychain to check if intermediate certificates are added (blue icon).

4. Install SSL Certificate:

   • In Keychain, locate the pending certificate request associated with your domain.
   • Drag the .crt file into this section to install it.

5. Assign Certificate to Services:

   • After installation, assign the certificate to specific services (e.g., Mail or web traffic) by selecting the appropriate options in Keychain during setup.

6. Verify Installation:

   • Check the list of installed certificates in Keychain.
   • Use online tools to verify SSL settings on your website.

7. Troubleshooting:

   • If issues arise, contact support for assistance.