Seems like a pretty neat application. I would suggest taking it one step at a time and working through it. Nobody is going to be able to walk you through the entire application in one forum post.
Start with creating users and allowing them to log in.
Then add the ability to upload .srt files.
Then create the system to navigate and view them... etc
Take it step by step and don't get ahead of yourself and we can try to help along the way.