Entry In Family Register
noun, verbal noun
Remember how 戸籍 is the family register? This is referring to that, and that makes this word mean entry in family register.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
結婚式の前に入籍をする予定です。
We are planning to be entered in the family register before the wedding ceremony.