Show all users:

SELECT user, host FROM mysql.user;

Create user:

create user '<user>'@'<host>' identified by '<password>';

Add permissions to the user:

grant all privileges on '<db-name>'.* to '<user>'@'<host>';

Delete user, drop user or user remove:

DROP USER '<user>'@'<host>';

Change user password:

ALTER USER '<user>'@'<host>' IDENTIFIED BY '<new-password>';
FLUSH PRIVILEGES;

All this applies for mysql version:

5.7.27