It is not that hard but you will have to get your hands dirty :) It sounds like your Apache is currently only running the one site, which makes things a little easier.
Get Apache to start. In general, you enable as a service and it starts every time your computer starts. The exact command to do this depends on your operating system but most modern ones offer a 'Control Panel' or 'Configuration Settings'. Look for Services and either Apache or HTTPD under that.
The next is to figure out where your htdocs points to. That is controlled by a configuration file somewhere on your system, usually under /etc or /etc/apache2. The config is often directly in httpd.conf or default-server.conf.
For example on my system, file /etc/apache2/default-server.conf has a line that says:
If you copy the contents of public_html directory to that folder, then your website should be accessible. Make sure it is at least world-readable so that Apache can read it. You can reach it using http://127.0.0.1 or the name of your local machine.
There are tons of configuration reasons why the above may fail, so you consider this a starting point and do ask follow up questions as needed.