Here's a task to get you started. Building your library will require you to think deeply about the things that have happened to you through your career. I recommend taking a notepad, or opening a blank document, sitting in a comfy chair, and setting aside an hour. So, why is this a good idea? The fact is that remembering the highlights of your careers is difficult. This is because we generally interact with our memories in two ways, when we make them and when we remember them. When we make memories, we make them in the context of where we were and how you were feeling. Because of this, we usually remember things better if we're in the same place that the memory was made, and feeling the same things. So sitting at a computer trying to remember these stories can be really difficult. Instead, trying to remember what it was like sitting at your old desk, or leaving work after finishing a particular project for instance, can help to remind you of these stories.
If you want to develop this idea a little more, try giving your stories names. Your library is there to help you when you don't have the perfect answer prepared and ready to go. What this means is that, when you need to rely on your library you'll likely want to find an appropriate story quick. By giving your stories names you give yourself a way to quickly sort through them and eliminate, or identify a suitable story for the question you're answering. A story's name could be the place it happened, the project you were working on, or a person who was central to it. If you are talking about a time that you helped a colleague called Dave, then that could be "The Dave story". Or that time you spent all night trying to learn how Microsoft Excel works, that could be "The Excel story".