(I'm not trying to be pedantic, but if someone is having trouble finding the button, the exact text is helpful.)
Also, here's where the button takes you: https://deepmind.google.com/science/weatherlab
https://i.imgur.com/IVv4y0n.png
Keep in mind both button are "the demo". One is for trying out the API yourself, the other is for seeing a pre-made dashboard.