jQuery Grid Plugin – jqGrid

I'm using a codeigniter library which configures grid functionalities and builds the grid.

my application is already developed using table i'm implementing same functionalities into the grid.

actually i just need to know how can i populate the data which is posted back from the server using ajax post method!

the data which i get is something like this which is already json script,

{"rows":[{"id":"28","cell":[null,null,null,"28","TSG225","Lastname"]}],"cols":[null,null,null,"28","TSG225","Lastname"],"page":false,"total":1,"records":1}

please help me!