Note: There are TWO certificates that need to be installed during this process. The first is the "Site" certificate, contained in the email from Comodo. The second is the Intermediate CA certificate; please use the Intermediate CA certificate that came with your site certificate in the zip file. Please follow the steps below:

If you already have a temporary certificate in your /ServerRoot/ssl/certs directory, move, rename or delete it. Run the command "getca servername" where "servername" is the same name created during generation of the key or certificate request ("genkey servername" or "genreq servername"). Open the site certificate in the e-mail from Comodo with a text editor and copy the content (including the lines below), as shown below to your clipboard:

"-----BEGIN CERTIFICATE-----"
and
"-----END CERTIFICATE-----"

Paste the contents into the terminal window where you ran "getca".
Enter Control-D or the appropriate EOF character for your terminal.
Before restarting the server please install the intermediate certificate as below.
Use the Intermediate CA certificate provided with your site certificate and copy the certificate content (including the lines below), as shown below to your clipboard:

"-----BEGIN CERTIFICATE-----"
and
"-----END CERTIFICATE-----"

Paste the content into the file "ssl/certs/ca_new.txt" located in your ServerRoot directory. Change the SSLCACertificateFile directive in your httpd.conf file to point to the intermediate CA file (ca_new):

SSLCACertificateFile ssl/certs/ca_new.txt

Now restart the web server so that the new certificate is loaded