I think the must difficult part of use a BAPI it's FIND IT, you can use the TX: BAPI, but if you're looking for a tutorial to implement it, i think if you know how to use the SE37 Transaction you don't have any problem using a BAPI (after you know wich one you have to use).
Every BAPI inside the SE37 has a documentation about the parameters you need to pass it, because the parameters change in every BAPI.
