How I can drag objects(songs) into the game(at runtime) and save it?

In my game I want something that allows that drag songs that you have into the game during the runtime and when you stop the game the song appears in project. So in the internet a person could drag a song that he has and put it in the game and when he open again the game there would be the song there.

Note: I'm only asking about drag a song and save it to the project, the thing of the internet wa only an example.

Please if someone know please answer and if another person knows a different way please answer.