You can still do that, but you don't have to with the addition of Discover functionality. Simply click the new button and tell NotebookLM what you're interested in learning. Google says the app will consider "hundreds of potential web sources" in the blink of an eye,

The new Discover feature will find reference materials online based on topic descriptions.

Tired of spending hours hunting for sources for your reports or other projects? Google's AI-powered notebook can do that for you now. Here's how it works.