When you installed your distribution of Linux, the networking was configured. You probably already have an active eth0 from that initial configuration. This configuration is probably adequate for your use right now, but you may need to make changes over time. We will cover different configuration items related to IP networking and the files and tools for working with them.
Webmin offers a good set of network configuration tools under Networking, Network Configuration. You can configure individual interfaces and adjust their current settings or their saved settings. Also the Routing and Gateways, DNS Client settings, and local host addresses can be configured. Once all of the configurations have been edited, you can apply them by clicking Apply Configuration. Rebooting the system is not necessary.
Each distribution has its own tools for configuring network settings. You should consult your particular distribution's documentation to see what it uses. Each tool provides essentially the same configuration options as the Webmin tool. Some of them may provide options specific to the distribution.
Manual configuration is also possible, but it is a very deep subject. Please refer to your distribution documentation and the Resources at the end of this article for information about manual network configuration.