XAMPP port 7070

[JamesKohls]

I'm very new to using xampp, and have been watching many youtube videos on setting up xampp. My father runs a small business and after some bad experiences with past web designers/maintainers, asked if I could try and set up a mirror of his site, from where I can learn and maybe take over the running of the site. I've got it online, but many videos I watched instructed me to change the listen port to 7070 or 8080, so when connecting from a browser It requries I add the port number to connect, examplesite:8080. When I tired leaving the listen port in the httpd.conf file as 80, the website will not connect with my DNS name, but only connect with the IP address. Any explanation/ friendly advice would be greatly appreciated!