That string should alternate in and out the inner band. It
should not touch your head, ie. outside the outer padding.
The camp netting need to be trimmed. When it is tight on the helmet
(it should be), the exposed nettings should be cut away.
In the beginning, you can tie the string anywhere. Like at the back
or side, where you find the ring which the side strap supposed to
go through. The string should be long enough so that you have
leftover length and you can end it at a convenient place.