There are some differences in between Mac and Linux(CentOS) for my.cnf and some command line interfaces.

For your information, below is based on MySQL 8 and Mac OS X.

If you need to modify my.cnf, you will need to create it by vi /etc/my.cnf

#
# created by Chun Kang 2020-03-09
# based on the guide at https://confluence.atlassian.com/doc/database-setup-for-mysql-128747.html
#

[mysqld]
character-set-server=utf8mb4
collation-server=utf8mb4_bin
default-storage-engine=INNODB
max_allowed_packet=256M
innodb_log_file_size=2GB
transaction-isola

Start MySQL

sudo /usr/local/mysql/support-files/mysql.server start

Stop MySQL

sudo /usr/local/mysql/support-files/mysql.server stop

Restart MySQL

sudo /usr/local/mysql/support-files/mysql.server restart

Set root access permission from all hosts

cd /usr/local/mysql/bin
mysql -u root -p mysql

If you see > prompt, you can change it by below

update set host='%' from user where user='root';
flush;

If everything is okay, you can check it as following

select host, user, grant_priv from user;

+-----------+------------------+------------+
| host      | user             | grant_priv |
+-----------+------------------+------------+
| %         | root             | Y          |
| localhost | mysql.infoschema | N          |
| localhost | mysql.session    | N          |
| localhost | mysql.sys        | N          |
+-----------+------------------+------------+