Prayer to the holy Spirit to reveal your hidden faults and sins ,say the mortal or grievous sins you have committed in your whole life first ,or a (general confession whole life sins briefly or you may sit before the blessed sacrament and write it down on a paper ) be honest and do not hide anything from Jesus,repent and humble yourself make a through examination of conscience.
Before celebrating the Sacrament of Penance, one should prepare oneself with an examination of conscience, which involves reflecting prayerfully on one’s thoughts, words, and deeds in order to identify any sins.
There are various types of examinations of conscience but regardless of which one you use to prepare yourself for the Sacrament it should be rooted in Scripture; particularly, the Ten Commandments and Beatitudes. Below are a few examples of Examinations of Conscience that can help you prepare for the Sacrament.
Examination of Conscience based on the Ten Commandments
Examination of Conscience in Light of Catholic Social Teaching I En Español
Examination of Conscience for Children
Examination of Conscience for Young Adults
Examination of Conscience for Single People
Examination of Conscience for Married Persons