PO creation through third system

Hi Friends,

We have one process wherein PO is created in thirdparty system & that is being created in SAP through RFC call. Middleware used is Biztalk.

Now we have new third party system ( BOL) which need to do same job of PO creation. I want to know how process flows while integrating third party system to SAP .What are the details I will require from tool BOL etc. Is there any standard process which I can follow to get this done.

Thanks,

Kiran