At its simplest, you may have users connecting to your data base with terminal windows and interacting with MySQL as text over a LAN, but more likely, you're talking about LAMP (Linux-Apache-MySQL-PHP), where users connect with a browser to a web page and interact with forms.
In the simple case, you enable networking in MySQL on your data base server and everybody connects with SSH. That's discussed in MySQL documentation.
LAMP is the more common method (and much easier on users and you, too) where your web page (the Apache part) interacts with the data base with PHP doing the queries and handing the result back for display. There are all kinds of books, courses and tutorials available for PHP (many books include sample applications on CD-ROM/DVD that you can build on). Those materials demonstrate how to configure Apache, how to configure MySQL and how to construct PHP queries and displays in a web page. It would probably be a big help to look around for books and tutorials for PHP, starting, perhaps at http://www.oreilly.com/
along with reviews at http://www.amazon.com
. Google for PHP and take a look at a few of the results to get a feel for it.
Keep in mind that many web pages you view (such as Amazon and almost every shopping site) make use of PHP. It's not difficult, but it is a different way of thinking that will take a little effort on your part -- thus the suggestion to buy a book or two (after reading the reviews) that will show you what to do, how to do it and guide you as you go.
Hope this helps some.