use yast2 to configure the DSL/ADSL modem and to setup .
you have to setup the DSL LAN "ip" and "dns" and/or "default gateway" address for that "eth0" interface (all information is provided by you DSL Internet service provider , if not then ask for it.), which will be used to negotiate the connection and username+password when you dial for the connection.
Once you have setup the modem/LAN ard by Yast2, then run "KInternet" ("kinternet" from shell / terminal). The main window might be already running in the taskbar(?) in the right pan of the panel , left to the clock. Place the mouse over all icons present to hover/popup it's name, where you can identify the program. Right clicking the icon will bring menu which can be used to do the following :==>>
You have to define the interface "dsl0" (which is the default ) and setup the proper settings.
After that from Kinternet you create a dial up account.
then right click on the KInternet icon and click "Dial-in" to connect and "Hang-up" to disconnect.
It will be best to ask a general guide from your ISP for Linux setup.
Hope it will help.