At the beginning of the mission, you’ll be told to go and meet up with the rebels at Utkarsh. Once you get there, go inside the marked building and watch the ensuing cutscene. You’ll now be chasing down Pagan Min, so rush to the gyrocopter and start following him. Your ultimate goal is to kill Pagan Min, so make sure you have a decent sidearm.
Now, this can be over in a minute or it can last longer than expected, with it all depending on your weapon. If you happen to have the grenade launcher sidearm, then this mission will be over quickly. Otherwise, you’re going to likely have to wait until Pagan stops, which will take a good while. Once you manage to kill Pagan, the mission will be over.