How do to get to light sensor that is in the very

It is called the ambient light sensor.
You have to remove the instrument panel top cover.
To do this you have to first remove the instrument panel trim plate.Pull it off carefully.
If your truck is an automatic,apply the parking brake,move the shift lever all the way down and tilt the steering wheel down to enable removal.
Next remove the left & right side end panels,the right side air vents & the assist handle.(The release tabs are accessed through where the vents were)
Remove the left & right windshield trim moldings by pulling straight out.
Remove any bolts retaining the trim panel and lift it up.
Turn the light sensor 1/4 turn to remove it.