Ozzy, you can simply send us your workbook to our email support address, and we'll give you some coding techniques you can use to implement your task.
In the general case you should use the TreeCol property to specify the column which will show the tree structure (most likely, it is the 1st col), and use the RowLevel property to specify whether it is a parent (0) or a child (1) row.
Find also the 'Tree Grid: General Concept' topic in the Tree Grid section in the Programmer's Guide. It contains a good and comprehensive description of the tree creation process in iGrid.