[MM3-users] How to change the language in mailman3

Hi everyone, from here: https://hosted.weblate.org/projects/gnu-mailman/hyperkitty/it/ I see that there is a way to change the language of mailman3, postorius and hyperkitty But I don't find how. I read that you can download the .po files for the chosen language, but I didn't understand how to use these files. Could anyone show me how to do it?

Thank you in advance. Max