The best way to answer this question is to provide a personal example. Give a brief overview of a time when you were assigned a task that you weren't familiar with and then explain the steps you took to handle it.
For example, you could explain that you took the time to research the task and familiarize yourself with the requirements, and then explain if you asked for help or tried to solve the problem on your own.
Finally, explain the outcome of your actions and any lessons you learned from the experience.