[harmor19]

did you create the database in cpanel?

Well assuming you have cpanel login and click "MySQL Databases" link.
On the next page you see field for the database name

In this field type vbforum (it can be anything though)
Click "Add Db" and when you come to the next screen click the "Go Back" link

Look for

UserName: user123
Password: pass123
(of course you can change the username and password to anything you like.)
Now click the "Add User" button then click the "go back" link

You should see two drop down boxes with a dozen checkboxes (pictured below)


Note: you may have a prefix before the database name and username

Our database name is "prefix_vbforum" and our username is "prefix_user123"
On the left drop down menu select "prefix_user123" and on the right select "prefix_vbforum"
Now just click the button named "Add User to Db" and that's it.

Now in the config.php file
$dbusername = 'prefix_user123';
$dbpassword = 'pass123';
$dbname = 'prefix_vbforum';