In 12c you don't use carbundle psu apply now this is all done using datapatch.
Oracle Support:
Datapatch Known Issues (Doc ID 1609718.1)
Datapatch: Database 12c Post Patch SQL Automation (Doc ID 1585822.1)
cd $ORACLE_HOME/opatch
./datapatch
When complete
To check the PSU applied to your database using the following SQL statement
select * from DBA_REGISTRY_SQLPATCH;