Load hierachy to InfoObject with Flat File (BI 7.0)

Hi

I have a Dept Info Object with hierarchy.

I want to load the hierarchy (Parent Dept, Child Dept) from a flat file.

May I know the steps on loading the hierarchy ?

My flat file format is :

Parent_Dept;Child_Dept

123;456

122;455

..... etc

Btw I am using BI 7.0.

Thanks in advance !