Hi Reza,
Happy new year 2015.
central instance doesn't prompt for export file ( System copy file from source system),
db instance require export file.because export file contains actual data.
i understand that yours is distributed system.central instance is in one server and db instance is in another server.
1.Install central instance(required cd's swpm,kernel are main)
2.Install db instance(required cd's rdbms,swpm,kernel,export file ( System copy file from source system).
in this server install the structure of rdbms first.
as per my knowledge.
and read the Master installation guide from service.sap.com
Regards
vittal