You'll get an idea when you see the list of competencies, but they should be questions like the one ShowOfHands mentioned, eg
Tell me about a time you had to establish a working relationship with others [maybe outside your team]
... time when you had to adapt your communication style for different people
... time when you had to manage conflicting priorities
A decent interviewer should ask for the situation first, and then follow up with, what was your role? what was the outcome? what did you learn from the experience? etc etc rather than ask for the whole lot in one go.
It would be useful to prepare some examples of things you've done before the interview. They don't need to be earth-shattering, think of anything you've done that you're proud of even if it seems like a fairly minor situation. Remember to stick to what you did - don't fall into using 'we'.
Just talk naturally, don't think you have to use management jargon. I do competency-based interviewing regularly and it's annoying when people feel they have to get certain management phrases into the conversation when I just want to hear about what they did.
Best of luck, I'm sure you'll be fine