How do you correctly quote this Meanwhile the narrator tells us that they then girt him Beowulf in martial mail nor mourned for his life?

To correctly quote the text you provided from Beowulf, you would write: "Meanwhile, the narrator tells us: 'they then girt him Beowulf in martial mail nor mourned for his life.'" Make sure to include the quotation marks for the direct speech and properly attribute it to the narrator.