I like surfing on iTunes to find movies that I like. I intended to buy a lot of movies, but most of them do not have my language subtitles. I would like to sign up to subtitle movies on iTunes so there'd be more content available in my language.
Windows 10
If you want to provide subtitles for films you would have to contact the film studios, Apple doesn't add subtitles (nor do any other changes) to films (nor TV programmes)
Not sure what you mean by 'sign up to subtitle movies', but whether a particular film has subtitles is controlled by the rights-holder and what they put in your country's store.
Ah, I mean sign up to translate movies in my language.
How to sign up for subtitling movies on iTunes
