how to create a bapi to update and add record 2 abap r3 table created by me

i have created a abap r3 table and i now want to insert records into it through SAP netweaver(Web-Dynpro). So i need a bapi to udate and insert records in the abap r3 table.if someone can please tell me how to create the bapi..coz i handel the EP part and dont know much about abap.