"You should carefully read the output, especially the
recommendations at the end. It shows exactly which variables you
should adjust in the [mysqld] section of your my.cnf (on Debian and
Ubuntu the full path is /etc/mysql/my.cnf). Whenever you change
your my.cnf, make sure that you restart MySQL. You can then run
MySQLTuner again to see if it has further recommendations to
improve the MySQL performance. This way, you can optimize MySQL
step by step."