PEDNAME= PedCreateXYZ(PED.ID, X, Y, Z)
PedSetActionTree(PEDNAME, "/Global/FIGHTINGSTYLENAME", "Act/Anim/FIGHTINGSTYLENAME")
Example:
Sheldon = PedCreateXYZ(66,-507,322,31) -- Creates the ped
PedSetActionTree(Sheldon, "/Global/B_Striker_A", "Act/Anim/B_Striker_A") -- Change fighting style