code: @PostDeploy
    public void onDeploymentFinished(ProcessEngine processEngine) {
      long processCount = processEngine.getRuntimeService().createProcessInstanceQuery().processDefinitionKey(PROCESS_DEFINITION_KEY).count();
  
      if (processCount == 0) {
        // start an initial process instance
        Map<String, Object> variables = new HashMap<String, Object>();
        variables.put("taskName", "Camunda BPM evaluieren");
        variables.put("taskAssignee", "demo");
  
        ProcessInstance processInstance = processEngine.getRuntimeService().startProcessInstanceByKey(PROCESS_DEFINITION_KEY, "vorgang-27" , variables);
  
        variables = new HashMap<String, Object>();
        variables.put("subtaskName", "Evaluierungslizenz beantragen");
        variables.put("subtaskAssignee", "demo");
        processEngine.getRuntimeService().messageEventReceived("SUBTASK_WANTED", processInstance.getId(), variables);
  
        variables = new HashMap<String, Object>();
        variables.put("subtaskName", "Datenbank-Schema anlegen");
        variables.put("subtaskAssignee", "demo");
        processEngine.getRuntimeService().messageEventReceived("SUBTASK_WANTED", processInstance.getId(), variables);
  }
    }
docs: In a @PostDeploy Hook you can interact with the process engine and access
  the processes the application has deployed.