You have a couple of TV series or movies in English or any other languages stored on your Android device and want to add subtitles to them? Easy, here's what you will need:
A mobile app to download and add subtitles to your video files, in our case we shall make use of GMT Subtitles, which can be downloaded for free on the Play Store.
And finally a video player app that can read subtitle files. You can either opt for VLC or MX Player.
Download and install GMT Subtitles. Open the app and it will search for all the movies and TV series stored on your terminal and also determine which one of them already have a subtitle (the With subtitle or Without subtitle label is written below the title of each video):
By default, the application seeks subtitles in English, but you change the default language in Settings > Subtitles languages. Then return to the main screen, tap on the series or movie you want to edit and wait for the app to search for corresponding subtitle files. GMT Subtitles allows you to download subtitles files from Podnapisi.net, OpenSubtitles.org and other sources.
Once the search is over simply tap on the Download button:
Return to the main screen of the application and as you will notice the status of the selected video has changed to With subtitle. Click on the Play button and then select the video player app you want to use to view the video: