Not Allowed to Create User with Grant

I was trying to install wordpress on ubuntu using the link and struck at

When I run this command,I get the error-

GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP,ALTER
    -> ON wordpress.*
    -> TO wordpress@localhost
    -> IDENTIFIED BY 'root';


ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'IDENTIFIED BY 'root'' at line 1

I tried almost every syntax by changing the wordpress@localhost to 'wordpress'@'localhost'

I tried removing and adding the APOSTROPHE on 'root' in IDENTIFIED BY 'root',

then after searching I tried this command as well - GRANT ALL PRIVILEGES ON *.* TO 'wordpress'@'localhost' IDENTIFIED BY 'root' and got

Error - ERROR 1410 (42000): You are not allowed to create a user with GRANT

Nothing found working for me. Please help where am doing mistake. Thanks

P.S. Database is already there -

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| wordpress          |
+--------------------+
5 rows in set (0.01 sec)