How to modify the value in the registers in the BQ34Z100

(1)I'm using I2C to communicate with the BQ34Z100,but When I try to modify the value in the registers ? such as "DesignCapacity" …… 

(2)how to modify the value in the Data Flash,for example, the "Design Capacity" is in the class "Configuration",and it's subclassID is 48 with offset 21,how can I use these parameters to read and modify the value? I hope someone can tell me step by step ……

thanks