I'm no sure to understand, but do you want to make that example to work before running into more advanced one? or are you looking for a more complex example because you got that working.
If you are trying to adapt an UI that was built for another process engine you should:
1) Set up jbpm5 in the right way to be able to support the process execution + replace the API calls
2) fill all the VOs/DTOs that the other process engine is using to send to the UI with the information that you can get from jBPM5
3) see which bits were hardcoded by the other process engine to make the UI to work
With that you will be fine