When your certificate is issued you will receive 3 certificates:
Yourdomain.crt
ComodoClass3SecurityServicesCA.crt
GTECyberTrustGlobalRootCA.crt
Add the ComodoClass3SecurityServicesCA.crt certificate as Trusted Roots:
Then attach each certificate in turn to your website's Key Pair in the following order. At this point your Key Pair will be black.: Yourdomain.crt ComodoClass3SecurityServicesCA.crt GTECyberTrustGlobalRootCA.crt
Your Key Pair will now turn green.
Stop and Start the server, your site can now be found using the https entry
OurSSL Certificates are recognized by 99.3% of all current browsers