You twist that silver piece with the tabs that is at around 2 and 10 o clock in the picture clockwise or counter clockwise maybe, a quarter turn . If you need a new bulb better to have the new one B4 you start. Looks like in the picture its (HID) for the Limited model trim, with a D4S bulb thats needed on mine. Look around page 436 in your owners manual to confirm the bulb size ? Not real easy to change compared to the Halogen type (9005) like on some model trim Avalons, but doable.

 

Check this youtube video out.