Pauses and Silences are Okay
There are going to be a lot of periods during an interview when there are going to be pauses in conversation or flat out silence. This can be initiated by you or the interviewer and in most cases either is not an indicator that something is amiss.
You can ask for a moment to think of an answer and during this time there is most likely going to be complete silence. This is fine and perfectly normal, don’t get distracted because no one is talking, use the time you have asked for wisely and think of the best answer or example you can give.
Be Calm
If the interviewer is taking notes (and most likely they are), be comfortable with the fact that there is going to be pauses in between questions and they try and write everything down. This is actually a good thing because it means they have liked what you have to say and want to remember it when they are later making a decision on who to hire. Don’t feel the need to fill this space, let them continue writing and wait for the next question.