매다 is fastening something around or onto you — a seatbelt, a tie, a guitar strap, a wrap around the head — and the verb before it says how: 안전벨트 챙겨 매고 'buckle up properly', 넥타이 고쳐 매는 습관 'the habit of straightening his tie', 기타를 바꿔 맬 수가 없잖아요. One line is the set phrase 걱정 붙들어 매라, tie your worries down, meaning stop worrying.