Click on "Images" and you'll see a "Add Poster" button

I did it but when i click the add poster button there's no function to upload image

I'd like also to add this plot "Tornato dopo oltre cinquant'anni di assenza nella natia Cuba, Tomas Milian ripercorre le strade dell'Havana e le tappe della sua carriera. Documentario/intervista a cuore aperto: Milian si racconta, fra storie private e aneddoti da dietro le quinte, legittimando il suo status di icona del cinema popolare e le sue incursioni in quello d'autore."

Ohh! My bad! When you click on the button, you should see the 'Upload a Poster' popup and a "Select Files" button. If that's not working for you, @Travis will have to look into it. It would probably helps to know which device/browser you use.

I'd like also to add this plot

I see you already did. "Translated Overview" is the right place for it.

When i click that button there's no upload popup, i think it doesn't work.

Another question: when i open this movie on Letterboxd i don't see any data (year, actor, director, plot..) except the title, but i added those info here on TMDB.

Are you saying clicking this button here, doesn't do anything? If so, what browser are you using? It is working correctly for me.

Re: Letterboxd, you'll have to contact them for support. I can't answer that question.

@FrancescoChello said:

Another question: when i open this movie on Letterboxd i don't see any data (year, actor, director, plot..) except the title, but i added those info here on TMDB.

There is a actor and a director right now. However, I think you forgot to add a release date. Letterboxd only use English overviews. Can you find/translate one?

I could translate because i didn't find an english plot, did you? I finally added a poster from another device, but i still can't see it on Letterboxd and i don't know why

I could translate because i didn't find an english plot, did you?

I didn't! It probably wasn't released in an English market.

I finally added a poster from another device, but i still can't see it on Letterboxd

There is a small delay before you can see the changes on letterboxd. Let's wait at least one day.