It should be localhost.
You should make a database in your cpanel.
You should then make a database user with a password (this can be found just below where you made the database).
You then need to link the database user to the database - this can be done by the part just underneath. You'll also need to give the datebase user permission to access the datebase. This is pretty much self explanatory on the page.
Then in your file, you just need to fill in the details it asks for with regards to the stuff you just made.