Most Content Management Systems (CMS) powered Websites require MySQL database on installation. This database can be created using the following:
go to CPanel, then locate “MySQL Databases” panel.
1) create new Database (enter text like db or web)
2) create new USERname (enter text user name and password)
3) give rights for this (select Database User Name) over (select Database Name from drop-down menu), check give all rights.
Now, note that the username and database name have been prefixed by your CPanel username and underline. Make sure you copy that to the website installation prompt the exact same way.
If you still get error you then most probably you missed a step or you typed the username and database name without the correct prefix.