You add the .idx file as the subtitle file. The .idx file itself points to the associated .sub file, so you don't have to tell ffmpegX about the .sub file. Note: this only works for encodings with the 'DVD mpeg2enc' preset and 'Decode with mplayer' activated.
Tonight is the night- Game of Thrones, season 6, premieres on HBO. The show begins at 8 p.m. CST, and will last for one hour.
GAME OF THRONES will appear on HBONow/Go at the same time as it airs on TV. However, the streaming sites are NOT a part of the free preview weekend. You will have to have a subscription in order to watch on the sites.