Indeed this probe does not have a very explicit instructions but after my research I came across the website of Arnaud Frich and with that I could perfectly calibrated (and in any simplicity) my screens. I first downloaded from the manufacturer's website the latest version of the software and everything was done quickly. The probe was positioned on the screen (the way to do this is very well explained and it is stable) and I launched the software.
Result: my photos are more faithful to the realities and I no longer galley in settings and other attempts to change color tone, with my photo processing software
And even if the screens of my relatives are not calibrated, the result is far better than before. (Especially from my Retina screen that is probably a bit too "flashy" and contrasted to the base)
In short, if you hesitate, do more and made bought this probe. You clearly would not be disappointed, especially if you make a lot of pictures (even an amateur like me !!