Make sure the Apache server has the open-source OpenSSL tool available.

• Locate the certificate, intermediate and private key files on the Apache server.
• Run the following command, substituting the paths and filenames where needed. You will need to enter a password that you will need to remember later.

openssl pkcs12 -export -in certificate_file -inkey private_key_file -certfile intermediate_file -out CertificateAndKey.pfx

• Copy the resulting 'CertificateAndKey.pfx' file onto the IIS server.
• Click 'Start', choose 'Run'. Type 'mmc', press 'OK'.
• In the MMC console, click the 'File' menu, and choose 'Add/Remove Snap-In'.
• Click the 'Add' button, then select 'Certificates' from the list and click 'Add'.
• From the next menu, select 'Computer account'. Click 'Next', select 'Local computer' then click 'Finish'. Click 'Close' then 'OK'. You will be back at the main MMC console.
• Expand the tree 'Certificates (Local Computer)' and click the 'Personal' sub-folder.
• Right-click and choose 'All Tasks' > 'Import'.
• Follow the wizard through, selecting the default options. You will need the password from the second step.
• The certificate will now be imported and available to IIS.
• Load the IIS Management Console, right-click the website you require the certificate installed on, choose 'Properties' and 'Directory Security'.
• Click the 'Server Certificate' button, choosing 'Assign an existing certificate' from the options.
• Select the newly-imported certificate from the list. Complete the wizard.
• The certificate will be installed and working on the site. A restart of IIS may be required to complete the process.