Hey Raffaella
Thanks for posting in the Lucid Community! Just to make sure that we are on the same page check out our Google Add-on article from the Lucid Help Center and let me know if you have any questions about the set up or intended functionality. If you’d like to see the functionality of Google Add-ons and what it looks like take a look at this Community Post (in English).
It should be noted that once the Lucidchart add-on is installed you will have a bar on the right side of your page that has the Lucidchart symbol. This is where you can go to insert your charts.
Hope this helps--please let me know if you have any other questions! Cheers