(Information and examples taken from the DroidScript documentation)

The GetPrivateFolder method gets the full path to a hidden folder on the devices internal storage, creating the folder if necessary. This folder will only be accessible from the App that created it.

 fldr = app.GetPrivateFolder( name );

See also MakeFolder

function OnStart()
{
  fldr = app.GetPrivateFolder( "MyStuff" );
  app.ShowPopup( fldr );
}