First we need to have an OSB proxy service with an WSDL.
As transport protocol we will use the SB protocol
Export the WSDL of the OSB Proxy service and put the wsdl and xsd's in your BPEL project.
When we take a look at the WSDL we can see that the OSB proxy service address is sb://xxx:70001/w..
In the BPEL project we can add a partnerlink, where we will use the OSB proxy wsdl.
You only have to add some assign process activities to fill or retrieve the input and output variable.