Hi @Sally_Knowles, since your question does not cover anything about what kind of problem you are facing, I am going to answer to the best of my knowledge.
Are you looking for feedback after each trial or are you looking for feedback at the end of the loop?
If you are looking for feedback after every response, the demo given by by @dvbridges works perfectly fine. Also the demo of ExtendedStroop in builder view works pretty well too.
If you are looking for feedback at the end of the trial loop, for builder view, this link is very helpful: https://www.psychopy.org/recipes/builderFeedback.html#feedback-after-a-block
or for coder view, Unable to give feedback on answers.
Hope this helps!