My 2002 Avalon key turn enough to unlock the steering wheel but cannot turn the car on. I tried everything that I read on this forum, but it did not work. So my conclusion is my cylinder is bad. How do you change the lock cylinder with the key just turn enough to unlock the steering wheel, if you are able to help I would be very grateful

Remove the left lower dash panel, look for a small hole about 1/8th diam in the key cyl housing. Have the key in and turn to ACC position. Push the pin in the small hole with a pick, and simply pull the key with the cyl all together.
Note: having the new part in your hand will help seeing the orientation of how the pin is positioned.
A locksmith can re key the new part to your old keys which I recommend.