More often than not you'll be asked to demonstrate a certain skill by providing an example of when you've used it, what happened, and how you utilised this skill to work on a particular task.
To ace this question you may like to use the STAR technique.
It can be useful to practice this technique prior to the interview so you can ensure you get it all in the right order.
Situation: Let them know the situation you were in.
Task: What did you contribute to amending the situation e.g. ‘it was my job to project manage the task’.
Action: What actions did you carry out e.g. ‘we did an analysis of where the problem originated and found a solution’.
Response: What were the results e.g. ‘we implemented the solution, achieving a 5% increase in customer satisfaction for that particular area’.