When you have finished, and generated your language pack --> you need to copy the generated files in the SolidCP Portal .

Once you placed them in there you need to add the language in the file: App_DataSupportedLocales.config

Thank you... I'm going to try it right now... I'll let you know if I was able to...

OK! I did it... I obtained the languages menu but I cannot see any difference once I login, the default language is still English. I copied the folders it-IT, es-ES, fr-FR in the root of c:SolidCPPortal and I changed the file you told me adding the other languages. Into the folders I copied I put the two folderd I got from unpacking the .zip generated, it means: "App_GlobalResources" and "DesktopModules". On more I left there the file that I found "Resources.xml"
Is there anything wrong in what I made?

If you copied in the contents of the Zip in the root of SolidCP Portal + added the languages to the file i mentioned above (do set Fallback language to en_EN) --> you select it at login it should imidiately change to your new language.

If things look the same to you after login i assume your pages are cached either in browser or in server side (try a iisreset && if you use chrome use shift + f5 to empty cookies)

Well, now in C:SolidCPPortal I have three folders like this: "it-IT", "es-ES" and "fr-FR". In each of those folders there are three objects: "App_GlobalResources"(folder), "DesktopModules"(folder) and "Resources.xml"(file).

My "SopportedLocales.config" looks like this:

[Locale name="English" key="en-us" fallback="" /]
[Locale name="Italian" key="it-IT" fallback="" /]
[Locale name="Spanish" key="es-ES" fallback="" /]
[Locale name="French" key="fr-FR" fallback="" /]

Is it wrong?
I'm using the square parenthesis because it doesn't let me post a code.