Use the following criteria to select the revocation configuration certificate:
If the certification authority (CA) certificate has been published to Active Directory Domain Services (AD DS) and the computer you are configuring has access to this information in AD DS, click Select a certificate for an existing enterprise CA.
If AD DS cannot be accessed and you know the name of the CA certificate and that it exists in the local root certificate store, click Select a certificate from the local certificate store.
This option is not available if the Online Responder is not on the same computer as the Online Responder snap-in.
If AD DS cannot be accessed and the CA certificate (with a .cer extension) is available on removable media, click Import certificate from a file.