Should be in your owner's manual or you could do a search... I'm just letting you know because believe me you'll be hearing it from others if I don't. (and maybe even if I do

). Anyway, I think you set the odometer to trip A but if not it's to odometer. Turn key off. Hold trip button in and turn key to 'on' (not start). I believe 5 dashes appear and then go out one by one. Once it's complete you can release the button and turn the key off. Light should be reset until 4.5K miles when it will blink for the next 500 miles and then go solid. Anyway that's how it works on my Camry.