Cannot add a new MySql database

Hello
I realise the error I am getting has very little to do with Webassist but am hoping someone may have some helpful information perhaps "been here before"!
I am using xampp with DW CS6 on XP

I am also using Navicat and have 3 sites with mysql databases all working OK on my local machine.

I decided to create another mysql database but am having difficulties.

In Navicat I went to create a new database and entered a name but received an error message
1144 Access denied for user 'root'@'localhost' to database 'Mydatabase'

I selected Manage Users and received the error
1142 SELECT command denied to use 'root'@'localhost' for table 'user' as far as I can see there is no table called user.

If I right click existing and working database and the select Manage users I get the error
1142 SELECT command denied to use 'root'@'localhost' for table 'user'

I put the question to Navicat and they came back with the following suggestions but I cannot find where to run their suggestions.

GRANT ALL PRIVILEGES ON *.* TO 'YourUserName'@'%' IDENTIFIED BY "YourPassword";

or

GRANT ALL PRIVILEGES ON *.* TO 'YourUserName'@'YourIP' IDENTIFIED BY "YourPassword";

I cannot open phpMyAdmin as I get errors.

Sorry if placing a mysql question here is out of order.

Thank You

John