Install

Ubuntu packages are available in the official repositories.

If the latest version isn't on the official repositories yet, it should be available in one of the following:

WebUpd8:

sudo add-apt-repository ppa:nilarimogard/webupd8
sudo apt-get update
sudo apt-get install gnome-subtitles


Gnome Subtitles PPA:

sudo add-apt-repository ppa:pedrocastro/ppa
sudo apt-get update
sudo apt-get install gnome-subtitles


Run

Use the icon in the Gnome Menu or run it from a terminal with:

gnome-subtitles