GNOME and its forks, i.e. Unity, Cinnamon, etc. uses GNOME Network Manager. You can easily connect to the internet using the DSL connection.
- Right click on the NetworkManager Applet or nm-applet. In some systems, it would be named as Network Connections.
- Select Edit Connections.
- Go to DSL tab. Select Add.
- Go to PPP Settings. In the Authentication section, keep PAP and CHAP as selected methods and unselect the rests.
- Now go to IPv4 tab. From Method, select Manual. In Addresses, Add Address, Netmask and Gateway. Write down the DNS server address in the respective field.
- Now go to DSL tab and put down your username and password. No need to provide with your Service name. Now Save it.
- It would appear in Network Manager Applet just afterwards. Select it from nm-applet. You would get connected to the Internet.