BODS datastore configuretions for SAP aplication

Hi,

When we are create a data store for SAP application, In advanced option we need to mention data transfer method .

In BODS 4.1 we have 5 types of methods are there in those, i want know how to configure for 1.RFC ,2.Direct down load and

3.custom transfer methods.

For custom transfer method where do we create custom program ??

we are using BODS4.1 on Windows

Thanks,

phani