Have apple tv2 have home share don't know how to open port 3689

Have apple tv2 . Home share is set up .using windows 7. When I press menu,no list is seen under computer menu. Apple suggested I open port 3689(?). How do I do this ?

Have apple tv2 . Home share is set up .using windows 7. When I press menu,no list is seen under computer menu. Apple suggested I open port 3689(?). How do I do this ?