There are quite a few simple examples in the manual. I think if you really read into it, you'll start to understand.
What you need to do is check which answer they gave for the question, then you will check if this is the correct answer and depending on this show the message you want to create.
Let's say, for question with the code Q1, answer code 1 is the correct one, you would do something like this:
Code:
{if(Q1==1,"Great, your answer is correct", "Unfortunately you gave the wrong answer")}
This is not a tested example and I am not sure if the code is 100% correct. It is just to give you an idea where to look at.