Create MySQL Database & User
If you don't understand what the following commands do, please refer to the guide from Pterodactyl.
mysql -u root -p
CREATE DATABASE billing;
CREATE USER 'pterobilling'@'127.0.0.1' IDENTIFIED BY 'password';
GRANT ALL PRIVILEGES ON billing.* TO 'pterobilling'@'127.0.0.1' WITH GRANT OPTION;