Short answer: Go to the DMV in your area with his Passport (including his visa documents) and ask to apply for a driver’s permit. They’ll step you through it. If he’s never been licensed before he may be required to do in-car training hours (depends on your state’s requirements, his age, etc.)
@LuckyGuy:Depending on where he lives he may be required to take the written & in-car test to get a driver’s license, regardless of whether he has an Int’l Drivers License.
I had a valid Japanese driver’s license (and an expired Ohio driver’s license) and was required to re-take the in-car & written test, for example.
Also, when I moved from Ohio to Minnesota and went to get my first MN Driver’s License I was required to re-take the written test (because laws can vary by state) but not the in-car test.
Our German exchange student applied for and got her Driver’s license while here (her birth certificate was not needed, she was able to use her passport as the required photo id) – but the State revoked it’s validity six months after she got it – as it coincided with her student visa expiration (which wasn’t a problem for her because she’d already returned to Germany by then).
As an international resident of the US the type and duration of his visa will impact his ability to get a license. If he’s only here on a tourist visa, for example, he’s unlikely to be permitted to get a driver’s license.