A basic configuration:

<IfModule mod_spkac.c>
<Location /spkac>
  SetHandler spkac
  SpkacSubjectRequest CN
  SpkacSubjectRequest 2.5.4.5
  SpkacSubjectRequest O
  SpkacSubjectRequest C
  SpkacSubjectSet OU "Terms and Conditions Apply"
#  SpkacSubjectRequest CN
#  SpkacSubjectCGI OU UNIQUE_ID
#  SpkacSubjectSet OU "Test Certificate"
#  SpkacSubjectAltNameRequest rfc822Name
  CASimpleTime on
  CADiskSerialFile /tmp/serial
  CADiskIndexFile /tmp/index
  CADiskCertificateBySerialPath /tmp/
</Location>
</IfModule>