Increase amibience in the materials menu for the easy way out. But for a real glow effect, duplicate the sword's blade and go into the material types (the little arrow to the left of the #1 material pop-up box). There, choose Additive and uncheck cast shadows and receives shadows. Change the material to a volumetric texture (click the green globe thing in the upper left-hand corner). Turn base density down 5-7% and turn edge softness and fuzzy factor all the way up. If you want the glow to pulsate, raise and lower the base density with each key frame.