Putting Subtitles on Android video players is easy as a pie. What you need is the sub file (SRT, SUB), a File Manager, and a video player. To add subtitle to a playing movie on Android, you just need to make sure, both video file and subtitle file are at the same directory, with the same file name (of course with different extension), and then enjoy watching the video with subtitle (On some video players, like the default Samsung Galaxy video player or MX Player, you can select the subtitle file, regardless of its location and name)
Update: How to Change/Replace a Subtitle on Android
So, what if you have already transferred 2 subtitle files and want to replace and change them? Do these easy steps to Manually add a subtitle and change it on Android:
1. Open MX Player application
2. Start playing the video file, you would like to manually add or change the subtitle
3. Go to Settings (Tap the 3dot button) and then open Subtitle.
4. Tap Open and now browse the Subtitle file to add it to the movie