I detected the flash is inserted but i don't know how to access the flash drive. Pls help.
RP/0/RSP0/CPU0:Jul 2 15:22:44.077 : umass-enum: Flash device inserted
Correct, note that you can't boot from rommon from it today, this is something we're trying to fix up.
Also reference the asr9000 turboboot and initial system bring up which has a dedicated section on the file system you may find interesting.