There's a test
Anybody who wishes to obtain a license to Apparate has to pass a test. From what's mentioned in the books this test appears to be comprised entirely of a practical assessment; the person undertaking the test has to demonstrate that they're able to Apparate both safely and accurately. There's no mention of a written theory component to the Apparition test, as there is for obtaining a driver's license in the UK (and, presumably, other countries).
“You have not, of course, passed your Apparition Test,” he said.
“No,” said Harry. “I thought you had to be seventeen?”
“You do,” said Dumbledore. “So you will need to hold on to my arm very tightly. My left, if you don’t mind — as you have noticed, my wand arm is a little fragile at the moment.”
Harry Potter and the Half-Blood Prince, Chapter 4, "Horace Slughorn"