You want to be a Catholic Priest. Keep that in your heart. But first learn to be Catholic, then your understanding will grow, and your desire for a priestly vocation may as well.
Go to Mass. Every day. Begin now. You will not receive the body and blood of our Lord Jesus Christ until your confirmation, but go before Him every day. And pray for patience, and humility. You will need both.
Go to adoration whenever possible. (There’s probably a perpetual adoration chapel in your area, or at least a parish that offers adoration fairly frequently.)
Learn first to be a very good Catholic, and submit yourself to God’s will and his Church.
Pray the Rosary, every single day. Pray for the strength to be a good Catholic, and for discernment towards your vocation to serve God and His Church, and to do only His will, regardless of what His will for you may be. Abandon yourself to His will. Ask our Lady to guide you on your path.
Read the Catechism of the Catholic Church, front to back. And then again.
Here > >
vatican.va/archive/ENG0015/_INDEX.HTM
Begin now.
Help the poor and/or sick. Devote some time to this. Begin now.
You want to be a Priest. Once you are confirmed as a Catholic then get close to the altar. I suggest becoming an Altar Server at your parish, this will include becoming a reader, and an Extraordinary Minister of Holy Communion.
Becoming a Server will help you foster closer relationships with the priests at your parish. If you do decide to pursue a priestly vocation then you will need your parish priests to give a recommendation once the Vocations Director inquires to them about you. Serve your Church and the poor in your community.
Once you are confirmed and serving Mass and doing charitable works then contact the Vocations Director in your diocese and set an appointment for your initial inquiry about possibly becoming a Priest. He will direct you from there.
Immerse yourself in your Catholic faith. Live it. Begin now.
Live a chaste life. Pray for purity and begin now tackling any issues you may have with this.
There is so much more, of course. This barely scratches the surface. Typically, as already mentioned, the Church won’t accept applications for seminary from neophytes, but I can tell you that exceptions are sometimes (though rarely) made, depending on the candidate.
First thing you want to do though is learn to be the best Catholic that you can possibly be. Focus now on that. Daily Mass, prayer, and study.
You are in my prayers, Justin. God bless.