Hello Cathy,
You'll need to create a program based on SRM function modules such as BBP_PD_SC_CREATE/BBP_PD_SC_CREATE_EXTERNAL and BBP_PD_SC_SAVE. This program would need to load the information from a flat file. Make sure of the inputs required by the FM's, as some fields are mandatory. Also, some fields might require previous configuration, such as product categories (material groups), because I believe that the FM requires the related GUID's, and not only the material group "code".
You might also want to check out the WSRM protocols for Point-to-Point Communication, if you are using PI-Independent Services. Related information can be found here: http://help.sap.com/saphelp_srm701/helpdata/en/01/6a4a057df0442ea34f054c8993add3/frameset.htm
Hope this information was useful.
Regards,
Gilberto Gallardo