Hi Aili,
Are you looking for the manual that describes the assembly instructions for the DSP568xx family? Or are you looking for the manual that describes the syntax, pseudo-ops and operation of the CodeWarrior assembler?
If you need the former, it is in the processor's reference manual:
http://www.freescale.com/files/dsp/doc/ref_manual/DSP56800ERM.pdfIf you need the latter, it is probably buried in a folder somewhere within your CodeWarrior installation. I can't help you there, as I don't use CodeWarrior.