First, create a new general and give him one of the following names for the desired stat
increase: (First the name, then bonuses)

DAMASCUS: All
DOJI: All
GUAN YU: Sword, naginata, horse and Archery
HONDA: Sword attack power
KABUKI: Spear, Naginata
KATO: Sword and spear attack power
KOJIRO: Weapon
KONDO: Spear attack, defense
KOTAROU: Sword and horse attack poweer
MUSASHI: All
MUSASIBOU: Sword, spear and horse
OKITA: Sword, spear
OYU: Spear, horse and Archery
SAKAMOTO: Sword, spear
SAKON: Sword, spear
SASAKI: Spear attack and ranged defense
SHIZUNA: Jumping, speed and Archery
ZHANG FEI: Spear