Most Americans never have to request a security clearance in the US and because they don't they are in the dark about the process.
I have had several positions in the Pentagon and need a higher than top secret clearance. When I was granted the clearance a security officer explained all the requirements of having a clearance and the need to protect the nation's security. After the briefing I signed a statement to the fact that I was briefed and that I understood the requirements.
People in the State Department received the same briefing and signed they understood. Apparently Hillary either lied about her briefing or worse didn't think protecting America's security was important. The private server was a violation of law and process for handling top secret and above information.
Additionally as a member of the Nations Security Council (NSC) she was in meeting discussing high security items. When she says she didn't know information was highly classified she lied. She was and will continue to be a danger to the nation's security and is unfit to become president of the county.