Our Lord said “Whose sins you shall forgive, they shall be forgiven.” This is to say, God has given man the power to forgive sins through Jesus. As a result, the Priest have the authority to forgive sins. The barrier between man and God is Sin. Christ came on earth to bring peace to people of goodwill and devised a means of removing that barrier through Confession of sins.
The means by which God forgives sins after baptism is confession. “If we confess our sins, he is faithful and just, and will forgive our sins and cleanse us from all unrighteousness” (1 John 1:9) Confessing your sins to a priest is a way of admitting your wrong doings to yourself. It means you know what you have done wrong and you feel guilty about it and seek redemption.
New converts cannot receive Holy Communion without going through confession stage. The basics is that, confession and absolution must be received by a sinner before receiving Holy Communion, “for whoever eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of profaning the body and blood of the Lord” (1 Cor. 11:27).
If you decide to go to a proper Catholic priest in a church and confess; here are some guidelines for your initial confession.
This is the first time you’re going to a church as an adult to confess, there are going to be a number of things you might want to admit that you’ve done. Start with the Ten Commandments to properly examine yourself and your conscience or you can take the seven deadly sins approach. Pride/Vanity, Envy, Gluttony, Lust, Anger/Wrath, Greed/Covetousness, Sloth.
In case of the Ten Commandments, It is going to be hard to remember every sin you’ve decided to confess so it’s better to use a pen and a paper. Write them all down and then decide which one takes priority over the other. This is because of course going as a grown-up for the first time, the list is going to be long and the priest cannot give you a lot of time. Your confession has to be short. So, you have to decide what sins you need to confess. There’s no need to go into great detail, just confess the sin!
If you don’t want to be rushed, try going in the end. Let other people finish their confessions so there’s no one waiting behind you and you don’t feel the need to hurry.
After the confession, it is better to burn the paper. It isn’t a good idea to hang on to your past sins. Just remember God forgives and forgets.
There is another major factor that has to be considered before going in. You have to know if you’re going as a catechumen (unbaptized) or a candidate (validly baptized). In the case of former you need to let the priest know that you were recently baptized before you begin confession. That is a good thing because a baptism is an immediate remission of all sin, including original, minor and mortal sin. Also you will not have to discuss any sins prior to your baptism.
In case of the latter, as I mentioned, the list is going to be pretty long. So according to Catholic practice, you need to consider the most serious mortal sins, to keep the confession from going on too long (the priest will, naturally, cut you off if it takes time). What you can do is let the priest know that you were baptized previously but entered the church now or you are in RCIA with the intention to convert to Catholicism Most priests will understand the dilemma and possibly grant you absolution for sins you could not confess.
First Time Catholic Church confession for an adult, try to prepare as best as you can. How to go to confession will give you good understanding to preparation. It’s always a great feeling to get that heavy burden off the shoulder, especially if you’ve done something wrong you feel you cannot reveal to anyone, in this case, a priest is the right person to open your heart to. However, confessing for the first time especially being an adult can be intimidating but it’s nothing to be afraid of. After the confession you will instantly experience a sense of relief and you will be at peace with yourself and with a high spirit the Lord has forgiven you.