2002 chevy silverado eninge light stays on,how can I turn it off

Engine light is on because the electronics have detected a fault and switched to an emergency programme.

The fault should be stored in the memory and a scanner or code reader is needed to extract it. The next step is to rectify the fault and clear the code which will extinguish the light.

You will need to either take the car to a place where they can diagnose it, or buy a diagnostic meter and do it your self.
Here in the US, most car parts stores will diagnose it for you, and will tell you the code of what is wrong.
A repair shop has a list of what each code number means, and may be able to 1) fix the problem, and 2) turn off the light.
Car parts stores also sell the meters that will tell you what is the problem, I bought one for $ 75.
God bless your efforts.