This is taken from one of my CPanel articles I wrote several months back. I think this is one of the more helpful topics as people often have problems with MySQL, so here it is.
How do I add a MySQL database in CPanel?
*This article assumes you are already logged into CPanel*
Adding a MySQL database: In the 3rd row, 3rd to the right you will see an icon labeled as MySQL Databases. Click on it.
This will take you to a new page where you will see:
In the box marked as DB, this is where you will enter the name of the database. Do so now and click on the button labeled as Add DB. The database will then be created.
Now, in the Username and Password boxes enter the username and password which will be used for to access the MySQL database. Once you have done so, click on the button labeled as Add User.
In the Host box, if the MySQL server is on the same server then type in localhost and click on the button labeled as Add Host. If it isn't, then enter the IP/server name instead.
You now have a MySQL database and a user. So now you must add the user to the database in order to access it. At the top of the page there are 2 boxes across from each other. One will have the username in it and the other has the MySQL database name in it. If they are not already selected, click the drop down box and select your user and/or MySQL database. Once you have done this click on the button labeled as Add User to Db.
The user is now added to the database and you can start using it.