How to create new DB user + DB and assign this user to DB

Login as an administrator

sudo mysql -u root -p

Create DB, DB user and grant privileges to the DB table

CREATE USER 'test'@'localhost' IDENTIFIED BY 'TEST123!password';
CREATE DATABASE test;
GRANT ALL PRIVILEGES ON  `test`.* TO  'test'@'localhost' WITH GRANT OPTION;
FLUSH PRIVILEGES;

Check

quit
mysql -u test -p
TEST123!password

use test;
show tables;