It is almost always a bad idea to manipulate a control on one form from another form.
However, if you want to do this directly, you merely need to change the access modifier in
the declaration for the listview in form2 from private to public.
Then you can reference the listview from the first form where you instantiate and display the form. Still, I want to make it very clear that this is commonly regarded as a very bad programming practice.
A better solution is to let the second form populate its own listview. There are numerous ways to do this, but one common way is to provide a method on the second form that is used to pass the list that you want displayed (by list here, I mean the array, dataset, or whatever you are going to use to populate the listview). For a dialog form, you would control all the behavior of populating the listview, showing the form, and then finally returning any required values to the first form as needed. There are other ways as well.
To go a step further, however, it would be worthwhile looking into a model/view/controller or other more decoupled architecture to investigate some better solutions.
Woody Z http://www.learntoprogramnow.com