Not sure if you have already found this out. This is what I did:
1. Define a change-set.xml in your classpath and define your assets - either from guvnor or files or classpath ....
<resource source='http://localhost:8080/drools-guvnor/org.drools.guvnor.Guvnor/webdav/packages/com.mycompany/myProcess.bpmn2' type='BPMN2'/>
<resource source="classpath:com/mycompany/process/myOtherProcess.bpmn2" type="BPMN2" />
2. Build your knowledge base as a regular classpath resource to your change-set.xml
KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
kbase = kbuilder.newKnowledgeBase();
Alternately, you can go to your guvnor package - build the package, and add the ChangeSet.xml as a URL resource and avoid step (1). Hope this helps.