Refer step 25 of this document to see how to create a web-service for your BRM ruleset.
Once the web service is ready, it can be imported anywhere for use.
1. In your BPM, right-click on the 'WSDL' folder and select 'Import WSDL'. You can import your BRM web-service here.
2. Then place an automated activity in your BPM process design and set the BRM service as the Service Reference property of the Automated activity.
3. Once this is done, you will see the Condition and Action values of your BRM decision table in the Input and Output mapping of the Automated Activity.
4. Map the values of BPM process context to the BRM condition values in the 'Input Mapping' and get the corresponding output in Output mapping (Action Values of decision table).
Refer step 12 in this document to see how to import a WSDL in your BPM Process.
Hope this helps.