Hi Aleks
When you create the connection from BitTalk to SAP, you will connect with an ID of some sort. That ID will register in the SAP Gateway (transaction SMGW). You need to create an RFC with the ProgramID as the ID in the gateway. All that is is a handle against which the connection is registered. Then you can test the RFC connectionfrom SAP to BizTalk. Once the systems are connected at a technical level, then you can look at sending the info from BizTalk.
Regards,
Graham