With Generic Mod Config Menu (recommended)
- In the Title Menu click on the Gear in the lower left corner
- Click in SAO Asuna
- Activate the option "EnableAsunaArmor"
- and choose the season in "Asuna Armor"


Without Generic Mod Config Menu

- Open the game once to generate the config.json file
- Open "config.json" in mod folder with notepad
- In "EnableAsunaArmor" change from false to true
- In "AsunaArmor" switch to the season you want 
- Possible season are spring, summer, fall or winter