First make sure that you have properly set the database (old one) and make sure the link is right. eg:http://yoursite.com
Secondly upload your new wordpress to your server but don't run it from browser yet. There is a file named wp_config_sample.php, rename it to wp_config.php and open it. There edit 3 things your database name, database username and password
this is where to edit.
// ** MySQL settings - You can get this info from your web host ** //
/** The name of the database for WordPress */
/** MySQL database username */
/** MySQL database password */
If the url in your database matches the url to your wordpress site. The should properly work with all your old stuffs.