Adding a vertical scrollbar to a jqGrid

I have a working jQuery jqGrid, but I need to make it add a vertical scrollbar when the number of records exceed the grid size.

I tried setting the grid size explicitly. I tried variou things.

I attached the shell of the code so you can get a 10,000 foot view.
Thanks.

 

$("#my_dialog").dialog({
        title: "My Windows",
        modal: true,
        width: 700, 
        height: 550,        
        buttons: {
            Cancel: function () {
                $(this).dialog("close");
            },

	    Add: function () {
             // code removed from here
                $(this).dialog("close");
            }
                $(this).dialog("close");
            }
        }
    }).dialog("close");

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