There should be a configuration for it in /etc/httpd/conf.d/ or /etc/apache2/conf.d/ directories. In addition to that the files should be installed somewhere in /var/www/. I'm not on debian so I can't verify to be sure.
Wordpress depends on a webserver and in all likelyhood in your case that web server is Apache httpd. You need to install and setup mysql (create a user and database). Then visit the wordpress URL to set up the database and other specific config options you desire.
e.g. here's mysql code.
CREATE USER 'wordpress'@'localhost' IDENTIFIED BY 'wordpress';
CREATE DATABASE wordpress;
GRANT ALL PRIVILEGES ON wordpress.* TO 'wordpress'@'localhost' IDENTIFIED BY 'wordpress';
Then when you're going through the setup for wordpress select localhost to be the database (mysql and httpd should be running), and then choose the user/password to be wordpress since that's what we set up in our sample commands.
Remember to set up a firewall on your system. If you don't have a firewall configured then your mysql database (default port 3306) is open to vulnerabilities and it will be easy to hack your wordpress and even possibly your system.
Personally I'd rather download the latest wordpress from their website and then manually install it within /var/www/. You never know when the repository package could be outdated or, even worse, automatically upgraded and break your blog. If you do it more manually you'll learn more about it and you'll have more control when upgrading versions where security is a high risk. Being a php app there is a high risk
running it. Therefore it is always recommended to pay attention to new updates and be diligent about upgrading to the latest stable bugfix release.