Sorry but as other said, your question is not clear. Here's my answer though. First, your modem may be a stupid modem( a bridge ), just able to transform wide band modulation over the phone line to Ethernet (or even USB). In this case, you may need PPPOE (or PPPOA) to log into your ISP's network. Second, your modem may have a support for PPPOE, though being just a modem (like, for example DLink DSL320B, or Netgear DM111P). Is this case, log into the modem's GUI using a web browser, and enter your login and password. Third, your modem may be a real router (like for example the Livebox we have in France, Spain, England...) with a DHCP server for a local network. Like previously, log into your router's GUI with a web browser and fill the required fields.
Maybe you need a GUI for PPPOE. It's already installed and can be accessed by double-clicking the network icon in the task bar.
