...
Open the Microsoft Management Console (MMC) by clicking Start->Run-> type mmc and hit [Enter].
In the Console window, choose File-> Add/Remove Snap-in..
Under Available snap-ins, select Certificates and click Add then click OK.
Select Computer Account and click Next.
Click Local computer: (the computer this console is running on) and Finish.
On the resulting Console window, select Certificates (Local Computer)-> Certificates-> More Actions-> All Tasks-> Import..
In the Certificate Import Wizard window, click Next to continue to import the certificate.
Select Browse to import the certificate and click Next.
After choosing the Security type files. Click Next to proceed to Completing the Certificate Import Wizard window and click Finish as shown.
The successful certificate import wizard window appears. Click OK to close the wizard.
For detailed instructions on how to configure the Windows system to trust the Federal Common Policy CA G2 (FCPCA G2) certificate, refer How to configure Windows System to trust the FCPCA G2 Certificate.
...