Well, you do have a basic web server running after installing xampp.
You see the orange welcome page, right?
This is in directory /opt/lampp/htdocs/xampp/
Into this you pour the html files you want published.
Post the I.P. adress your internet provider has given you, and we can check if it works for you.
If you want people to acces your IP-adress other than by the IP-number, you need to buy a domain name (like daemon.net) and have them point to your IP-adress. Thus we can write www.daemon.net
and access the pages on your PC.
If this isn't enough, then you need to find a technicial to help you.