I have made a copy of and edited the wp-config-sample.php file with all of the database details that should be in it (obtained from my host, and also created in mamp pro data user).
I have also replaced the unique phrases and corrected all $ with S as suggested by WordPress forum, forums here and tutorials.
I also then saved it as wp-config.php as suggested. When I then go to WordPress and say submit it says that the file already exists.
In my WordPress folder there is both the original sample file and the edited one I was asked to either create or edit. If I delete the sample page and submit it says I am missing a wp-config.php and need to create it. I put it back and it says the file already exists. I then edited the wp-config-sample.php file and just corrected the name as wp-config.php and still nothing I try or change works.
(I solved this problem as my root password in mamp pro was not the same as in the wp.config file, as soon as I had that corrected it all fell into place and worked :-))
sorry, i am not allowed to comment, but are you developing on a local machine or through a web hosting? I believe your in Mac. The safe bet here would be, for you, to delete the wordpress folder in the htdocs directory, untar it again there, and from the browser go to localhost/wordpress-folder-name and follow the wizard. (open up localhost/phpmyadmin to setup MySQL database)
If you want to put the wordpress in a live web host, then use ftp to upload the wordpress directory (you will have to change the settings). So, actually, unzipping a fresh copy of wordpress directly, and following the wordpress setup wizard online would be easy. For the MySQL database, use the settings provided by the host.
In these steps, you never have to touch the wp-config-sample.php nor wp-config.php file.