You will be receiving the following three files from comodo:
Intermediate CA UTNAddTrustServerCA.crt
domain/site certificate yourdomainname.crt
Or you can download root and intermediate CA files from here.
The file must be in PKCS #7 format in order to be imported into a Server Certificate object. The file must contain all of the certificates to be imported into the object (the root-level CA certificate(AddTrustExternalCARoot.crt), the intermediate CA certificates(UTNAddTrustServerCA.crt) and the server certificate.
The method to view the subject is to double click the certificate that we sent you, then click on the 'Detail' tab and go to the 'Subject' area.
Steps to successfully install the Certificates:
Import both the 'Intermediate CA
certificate' and 'Root certificate' into Internet Explorer. Do this by double clicking on each of the certificates and choosing 'Import'.
Note:Please make sure they are imported into the correct stores -- the 'Intermediate CA certificate(UTNAddTrustServerCA.crt)' goes into the 'Intermediate' store, and the 'Root certificate(AddTrustExternalCARoot.crt)' goes into the 'Root' store.
Double click the certificate that was signed by Comodo (which was the server/domain certificate you received from us), go to the 'Details' tab, then click on 'Copy to File'. Next, Select 'Cryptographic Message Syntax Standard - PKCS #7 Certificates (.P7B)' and select the 'Include all certificates in the certification path if possible' check box. Give it a file name, for example 'c:\\mycert'. This step will put all three certificates -- the Trusted Root, Intermediate Root, and End Server Certificate -- into one certificate.
Go to Console One and to the certificate that created the Certificate Signing Request (CSR). Go to the 'Public Key Certificate' Tab. Select 'Import', select 'No Trusted Root Certificate available', and then 'Next'. Import the Server Certificate that you created in step (2.) above which we gave the example name of 'c:\\mycert'.
After the import you should be able to validate the certificate and use the certificate.
The certificate is now ready to use.
Related Articles: Which is Root? Which is Intermediate?