How to download certificates from AD?

Someone can help me with download email certificates from AD?
I need to configure encrypted messages (SMIME)

On a Windows computer, open the Microsoft Management Console (MMC).
Add the Certificates snap-in for the Current User or Local Computer account.
Navigate to Personal > Certificates.
Right-click and select All Tasks > Request New Certificate.
Follow the Certificate Enrollment wizard to request a new certificate.

If its an email S/MIME certificate that you’ve got in Outlook, then this might help.