1. On the server click Start -> Programs -> Administrative Tools -> Office Communications Server 2007.
2. Expand the snap-in until you find the Enterprise Edition Server.
3. Right-click on the Office Communications Server where the CSR was generated previously and click Certificates.
4. Click Next, then choose to Process the pending request and install the certificate.
5. Browse for the Certificate file that you received from COMODO (e.g. yourDomainName.cer).
6. Once you have selected the Certificate file click Next.
7. Close the Certificate Wizard.
Your certificate is now installed and ready to use.