First of all you need have an IDE i used Eclipse You need create a jar with the java classes that is under salesforce You need than modify the file under activi-app/WEB-INF/classes/Salesforce.properties
Here you need add your Username , Password and security token, client_id and client_secret
after you make this than copy the jar that you created on activi-app/WEB-INF/lib/
Now restart activiti and copy the app that is in the project as well.