You will need a .P7B file with the certificates in it that you are importing. I assume you know how to get to this point. (Short answer: export the cert from IE without the private key.)
You put the .P7B file in the \windows directory on the PPC. You then use the registry editor to add 2 keys.
[HKEY_CURRENT_USER\Comm\Security\SystemCertificates \MY]
"InitFile"="\windows\userroots.p7b"
[HKEY_LOCAL_MACHINE\Comm\Security\SystemCertificate s\MY]
"InitFile"="\windows\userroots.p7b"
You then switch go to "Start"-"Settings"-"System"-"Certificates" and voila...your certificates will be imported by opening the application. The 2 registry keys will disappear. This is normal.