Select File, New from the menu or
from the toolbar to create
a blank network.
If the current network has been modified but not saved a
prompt will ask you if you want to save it before continuing.

Select File, Open from the menu or
from the toolbar
to open the load file dialog box.
Select File, Save
from the menu or
from the toolbar to save the network.
Select File, Save As
from the menu to open the save file dialog box.