In order to unlock these outfits, you need to have existing Tales of Graces F or Tales of Xillia save data on your system. The games do not need to be cleared, just the save data is necessary. Load Tales of Symphonia, then start a new game. As a thank you from Namco Tales Studio, when starting a new game, you will receive the costume sets before the opening cinematic.

Costume Set	How to unlock
Tales of Graces F Costume Set	Have either Tales of Graces F or Tales of Xillia save data on your system, then start a new game on Tales of Symphonia.
Tales of the Abyss Costume Set	Have either Tales of Graces F or Tales of Xillia save data on your system, then start a new game on Tales of Symphonia.
Tales of Vesperia Costume Set	Have either Tales of Graces F or Tales of Xillia save data on your system, then start a new game on Tales of Symphonia.
Tales of Xillia 2 Costume Set	Have either Tales of Graces F or Tales of Xillia save data on your system, then start a new game on Tales of Symphonia.
Tales of Xillia Costume Set	Have either Tales of Graces F or Tales of Xillia save data on your system, then start a new game on Tales of Symphonia.