how do i adjust backlight time on my iphone

Not sure what you mean by Backlight time. But you can adjust how long it is before your phone auto locks at

Settings> General > Autolock

There are choices from 1 minute to Never.

Is there a way to increase the length of time that the background light stay on. Mine stay on only 5 seconds before it fades. I am NOT talking about the Autolock feature.

Sorry, I forgot to write that I have a new Apple 5c.