Importing portal certificate in ABAP system

Hello ,

I am importing SAPLogonTicketKeypair-cert.cert into abap system using  tcode strustsso2 .

But when I click on Add to certificate list it gives me error "Error during import" and the message no is "TRUST008"

Please guide me.

Also how to check if it already exist?and if it already exist then do I need to enter the details in "Add to ACL".

Please guide me.

Thanks and Regards,

AKSHAY