It's time to actually get into the car with the monster you've raised. Fingers crossed.
For the safety of yourself, your car, and everyone else in a one hundred-mile (160.9 kilometer) radius, go someplace without a lot of other people around. Or cars. Or light poles. Or shrubbery. Or anything. If you could do this first driving session in a crater on the moon, that would be ideal. But the next best thing is an empty parking lot. Really empty. Shuttered strip mall empty. Why? Because your kid is going to mix up the gas and the brake his first time out and you want it to be scary enough that he doesn't ever do it again, but not so scary it requires repacking the airbags.
Once you've found the perfect parking lot, keep going back in every type of weather. Torrential rain, fluffy snow, even slippery leaves all pose driving challenges. For the new driver, the important thing is to know what these things feel like from behind the wheel. When they're comfortable on dry pavement, you can begin to teach them cool stuff like steering into the skid. And maybe even how to do doughnuts.