Before you do the import, run the catalog.sql or catexp.sql scripts located at %ORACLE_HOME%\rdbms\admin, which will install two most essential roles for import and export i.e., IMP_FULL_DATABASE and EXP_FULL_DATABASE. And next, grant IMP_FULL_DATABASE to the user doing the import. And finally run the IMP tool in console to do the import. Am I clear enough ? ;P

always,
gtcol