You should create your MySQL Databases first in order to create tables in it and use.
To create MySQL databases.
- Login to cPanel.
- Navigate to MySQL Databases.
- Create a database (if you give the database name as DB, the database will have the name yourcpanelusername_DB)
- Create a MySQL User (if you give the user name as user, the username will be yourcpanelusername_user)
- Add the user to the database you just created & assign permissions for the user.
You now have the MySQL Database and Username to access it.
Here are the details to connect to MySQL from your PHP Script
Host - localhost
Username - yourcpanelusername_mysqlusername
Password - <password you have given during creation of MySQL User>
Database - yourcpanelusername_databasename
Hope, this will help you.
All the best.