There are multiple ways to import certificates on Windows. The CA authority that issued your certificate will also have a guide you may follow which will be specific to the certificate you have.
The steps below are general and may vary depedning on how you originally received your cerficate. In order to import the certificate you need to access it from the Microsoft Management Console (MMC).
Prerequsites
- An existing S/MIME cerfiticate (.pfx) on your Windows PC
Import your certificate
- Open the MMC (Start > Run > MMC).
- Go to File > Add / Remove Snap In
- Double Click Certificates
- Select Computer Account.
- Select Local Computer > Finish
- Click OK to exit the Snap-In window.
- Click [+] next to Certificates > Personal > Certificates
- Right click on Certificates and select All Tasks > Import
- Click Next
- Click Browse
- Select the .cer, .crt, or .pfx you would like to import. Click Open.
- Click Next
- Select Automatically select the certificate store based on the type of certificate.
- Click Finish & OK
The certificate is now visible in IIS (Internet Information Services).