She got hers from her "qualifications," She slept first down the hall from the governor of Arkansas and later down the hall from the President of the United States that gave her a Top secret security clearance.
President of the United States has unquestionable authority to grant top secret security clearance to any person he deems fit. So when he was on the phone discussing tops secrets while Monica Lewinsky sucked his dick she was defacto approved for top security clearance