This creates a backup of your primary certificate called DigiCertBackup.pfx. Copy this file to your IIS Server.
Importing your Certificate/Private Key in IIS (from .pfx file format):
Start > Run
Type in MMC and click GO
Go into the Console Tab (or File) > select Add/Remove Snap-in
Click on Add > Double Click on Certificates and click on Add > OK
Select Computer Account
Select Local Computer
Click the + to Expand the Certificates Consol Tree
Right click on the Personal Certificates Store (folder)
Choose > ALL TASKS > Import
Follow the Certificate Import Wizard to import your Primary Certificate from the .pfx file. When prompted, choose to automatically place the certificates in the certificate stores based on the type of the certificate.
Close the MMC console. In the case that you are prompted, it is not necessary to save the changes made to the MMC console.
In your IIS manager, right-click on the site that you would like to use the certificate and select properties.
Click on the Directory Security Tab and hit the Server Certificate Button. This will start the server certificate wizard.
If you are asked what you want to do with the current certificate on the site, choose to remove it, finish the wizard, and click the server certificate button to run the wizard again.
Choose to 'Assign an existing certificate' to the site and choose the new certificate that you just imported.