Download by right-clicking and save-as. Then open with jupyter lab (you can drag-and-drop the downloaded file into jupyter lab)
Notebooks are stored in a shared repository on github:
https://github.com/RubendeBruin/DAVE-notebooks
You can clone or download all notebooks from there. You may also fork it, add your own contributions, and create a pull request.
It is also possible to view a static version of the notebook online without downloading them. For example: