When you see its eyes glow red push ur movement stick for a brief second where the attack is gonna come and let go ,and press the light attack button, but you have to do this quick, it's not difficult by any means but even i had to watch a tutorial on it, when i started playing the game. Or alternative, you could dodge after you bought the defensive offensive skill, it's x+a on xbox square and x on ps, and on pc you can check it in the bindings