‘-은/ㄴ 후에’ is used to describe what happens after a particular action. ‘후’ means ‘after’ and this grammar means ‘after ~ing’ in general. If the verb ends with a consonant, use ‘-은 후에’. When the verb ends with a vowel or ‘ㄹ’, use ‘-ㄴ 후에’.
● 한국에 온 후에 살이 많이 쪘어요. (I got fat after coming to Korea.)
● 주소를 쓴 후에 저에게 주세요. (Please give it to me after writing address.)