It depends what you want to change, policy attributes, include list, schedule etc so please be more specific.
bpplinfo — manage or display policy attributes for NetBackup
bpplschedrep — modify NetBackup schedule attributes
All policy information is contained in the netbackup\db\class\ folder with one folder for each policy. And subfolders under it that relate the different policy components. You can take a backup of the class folder so you can rollback any mistakes.