DSL

First you should check if the ethernet-interface was detected.
Start a shell ("Menu | Run | Rxvt terminal emulator") and enter the following command:
ifconfig

Can you see "eth0"?

If you can not see "eth0" enter the following command:
ifconfig eth0 up

To check if the ethernet-interface is available now, enter the following command:
ifconfig

Now you should see "eth0". Close the shell.
Start the program "Menu | Network | Roaring Penguin PPPoE ADSL". The program has four registermaps, which will be described below.

Registermap Basic

Connection Name: freely selectable name, e.g. the name of your Internet-provider
Username: ask your provider
Network: leave it empty
Password: ask your provider

Registermap NIC and DNS

Ethernet Interface: eth0
DNS Setup: From Server

Registermap Options

Allow use by non-root users: mark with a check. Use synchronous PPP: mark with a cross
Firewall: Stand-Alone

Afterwards press the "OK" button. A new window appears "RP-PPPoE". There are two buttons named "Start" and "Stop".

With these two buttons you can connect / disconnect the Internet-connection. If you press the button "Start" two green bars should be visible. Now you are online.

You can now open the Internet browser "Menu | Internet | SeaMonkey Webbrowser". Enter a URL and see if the Internet site is displayed.