The short answer is you pass a test. Different tests for different levels of operator / license / bands allowed.
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As I understand it, the test is sort of canned (like the alien citizenship test) in the sense that you can practice taking a number of prior tests, which have questions that will be the same or similar to the one you will be taking. There are also study materials. The entry level operators test is not too difficult to pass.
You are correct. However, I should disclose that while I have had substantial training with electronics, I have not taken the tests due to a lack of time and money for the toys.
“One expensive hobby at a time” my wife says. :-)