Daniele The first screenshot is just a picture on the web stie, it is not a program dialog. That is why nothing happens when you click on that button. Just scrooll the page up and down and you will see. This is just an illustration. Sorry for the confusion.
If you scroll that page down to the end, you will see there link to download CUDA Runtime Libraries. If you will install it and then restart Tonfotos, then process of photo indexing will be slightly faster.
However, this is all optional. You can just igonore it all with “Don’t remind me again” button.