Guide

1. Inside your spreadsheet, navigate to the top menu bar and click 'File'.

2. Hover your mouse cursor over the 'Download' option, then select your preferred file format. To avoid inconveniences later on, consider PDF or HTML.

3. Following that, configure the export settings and tap 'Export' in the top-right corner.

4. Head back to NotebookLM afterwards and click 'Create New'.

5. Subsequently, click 'Choose File' and select the newly downloaded spreadsheet.

6. After completing these steps, your notebook will be integrated with Google Sheets. You can now use the imported spreadsheet as a source of data.