1)http://www.oracle.com/technetwork/middleware/bpm/learnmore/bpmwebinarseries-361340.html (Collated BPM Webinar)
2)http://andrejusb.blogspot.in/2010/10/initializing-oracle-bpm-11g-process.html (Initializing Oracle BPM 11g Process Payload from Oracle ADF 11g)
How ADF BC and BPM Payload Interact
3)Building a sample BPM Process http://www.oracle.com/webfolder/technetwork/tutorials/obe/fmw/obpm/11g/r1/firstProcess/firstprocess_obpm11g.htm
In addition this should also help - http://andrejusb.blogspot.in/2012/10/oow12-oracle-business-process.html
In addition to what Sudipto already mentioned, here are my 2 cents. For any BPM (SOA or BPEL also) one of the core things is something called Payload. It can be as simple as a just one field or as complex as 100's of fields in a very complex XSD Schema. Read the below post casually just to understand Payload part and how that works in a BPM Process:
Start with Hello World BPM and take step by step approach. Do not jump into all the areas like Business Rules etc in the first place.
If you have ADF knowledge, you are almost there. ADF is the core part once the process is defined. The implementation of all the screens for each step (User Task) in a Process uses, core ADF Technology.
Regarding the BPM / ADF tie. You can think of it as being three layers - Interactive activities in a process, their corresponding human task and the ADF task flow invoked by the human task.
Oracle BPM processes can have interactive activities that are done by people assigned to a role in the process or are specifically assigned to them. An end user is assigned a work item instance when the task enters one of the interactive activities in the process that they are assigned to. When this occurs, new task appears in that end users inbox in the Workspace or WebCenter Spaces.
When designing the process, each of the Interactive activities in the process are associated with a human task when the process is designed. Each human task is associated with an ADF task flow.
At runtime, this means that when an end user clicks one of the tasks in their inbox, the human task associated with that Interactive activity in the process is invoked which in turn executes the ADF taskflow associated with the human task. When the taskflow is invoked it renders the ADF form associated with the ADF task flow to the end user inside of the Workspace.
One of the most confusing things is how the payload of the work item instance is rendered and how this can be used to retrieve ADFbc information that you are already familiar with. In addition to what Ravi and Sudipto sent you, here are a couple more blogs that might help show the relationship between ADF and the BPM process instance payload:
Using a BPM Process Variable on an ADF form to Retrieve Database Information - http://www.avioconsulting.com/blog/datwood/2012/06/19/using-bpm-process-variable-adf-form-retrieve-database-information-0
Using a Database Driven List of Values to Populate a BPM Variable - http://www.avioconsulting.com/blog/datwood/2012/07/02/using-database-driven-list-values-populate-bpm-variable