누르다 is pressing down on something, and the adverb says how hard: 이렇게 세게 누르고 있는 거 "holding it down hard like this", 칼등으로 납작하게 누르기 "flatten it with the back of the knife". It is also the verb for buttons and screens, including the one you need online: 하트 엄청 티 나게 눌렀는데 "I spammed the likes so he'd notice", 키패드를 빠르게 누르는 "tapping the keypad fast". 이렇게 누르다 fills most of these lines because people are demonstrating with a finger.