Step 1. Install the Server file certificate using Key Manager For Essential SSL certificate, in additional to your domain certificate you will be receiving 4 more files.
These files must be imported in the following order:

• Root AddTrustExternalCARoot.crt
• Intermediate CA UTNAddTrustSGCCA.crt
• Intermediate CA ComodoUTNSGCCA.crt
• Intermediate CA EssentialSSLCA.crt

Or click to download the EssentialSSLCA files

Go to Key Manager.

• Install the new IIS SSL Server certificate by clicking on the key in the www directory (usually a broken key icon with a line through it), and select 'Install Key Certificate'.
• Enter the Password.
• When you are prompted for bindings, add the IP and Port Number. 'Any assigned' is acceptable if you do not have any other IIS SSL certificates installed on the web server.
• Note: Multiple certificates installed on the same web server will require a separate IP Address for each because SSL does not support host headers.
• Go to the Computers menu and select the option 'Commit Changes', or close Key Manager and select 'Yes' when prompted to commit changes.
• The new IIS SSL Server certificate is now successfully installed.
• Back up the Key in Key Manager by clicking on Key menu> Export -> Backup File. Store the backup file on the hard drive AND off the server.

Step 2: Installing the Root & Intermediate Certificates:

• Your IIS SSL Certificate will have been emailed to you.
• The email will also contain four other Certificates: AddTrustExternalCARoot.crt (ROOT certificate) , UTNAddTrustSGCCA.crt (Intermediate CA certificate), ComodoUTNSGCCA.crt (Intermediate CA certificate)and EssentialSSLCA.crt(Intermediate CA certificate).
• Save these Certificates to the desktop of the web server machine.

It is essential that you have installed these four Certificates on the machine running IIS 4.You can download the EssentialSSLCA files from here.

• Once you have installed the Certificates, restart the machine running IIS 4.
• You must now complete one of the following procedures - the procedure you follow is dependent on the Service Pack that has been implemented on your machine running IIS4.

Service Pack 3:

• Install the above certificates in your Internet Explorer by opening each certificate and clicking 'Install Certificate'.
• You may then use this IIS CA batch file to transfer all root certificates from your Internet Explorer to the IIS (see Microsoft Knowledge Base Q216339).

Service Pack 4:

• Install the above certificates manually in a specific root store (you may also want to read (see Microsoft Knowledge Base Q194788):
• Install the Root certificate by double clicking on the corresponding file this will start an installation wizard
• select Place all certificates in the following store and click browse
• select Show physical stores
• select Trusted Root Certification Authorities
• select Local Computer, click OK
• back in the wizard, click Next, click Finish

Repeat the same for the UTNAddTrustSGCCA.crt, ComodoUTNSGCCA.crt and EssentialSSLCA.crt however choose to place the certificates in the Intermediate Certification Authorities store.

Service Pack 5:
Same as SP4.

Service Pack 6:
Same as SP5.

• Reboot the web server to complete the installation.