Hi Kang,
Have you checked the User Guide in the docs folder of DSPLIB 3.1.1 package. Click on the API reference link in that html page to look at description of APIs and their arguments. another option if the DSPLIB was discovered as an eclipse plug in in your CCS version, you should be able to open the DSPLIB reference guide by going into CCS->Help menu.
Let us know if you still have any issues.
Regards,
Rahul