how you get Holy Arts skills i'm quite headball. I somehow in the middle of the game yet doesn't have holy arts level up...
There is a book at the left side inside the Library on Insignia Way (far right of town), where you can study to gain Holy Arts exp +3 a day (need 100 EXP for Lv5); it doesn't consume the day's time period,
so you kinda are expected to just route to it every day reset for 34 in game days straight...
EDIT2: Thanks to TheXoxx, so the actual intended method is through the part time job at Buele Clinic southwest of Old King's Way, talk to the lady by the counter (not the doctor upstairs), each patient you treat that doesn't sexually harass you will give 1 Holy Arts EXP at the cost of 4SP per patient. As with most jobs in the game each action you take consumes SP, so you would (be able to) earn more exp at higher levels with a larger SP pool per day (which early on you will probably have to either split up between things like helping church followers for Sacred Duty exp)
EDIT: And then to actually level up and learn the skills after you have enough exp, go to the church bedroom upstairs and talk to the "Learn Holy Arts" on the table