"Always smile" - always: 늘 / 항상 / 언제나. - smile: 웃어 (smile, laugh) / 미소(를) 지어 (smile). So you can say: 늘 [항상, 언제나] 웃어 or 늘 [항상, 언제나] 미소를 지어.

actually you can see on the dectionary

If someone is upper than you, you can say like '항상 웃으세요[hangsang ususeyo]' or '항상 웃어 주세요[~~ useojuseyo]'<-more gentle If isn't, it can be '항상 웃어[hangsang useo]' or '항상 웃어줘[~~ useojuo]'<-more gentle Cheer up for your study![emoji][emoji]