You can set up your network using the CNSH-800 alone. However, as peterh indicated, to set up a connection so that your network can share the ADSL connection, you will need a Cable/DSL router. Again, presuming your ADSL modem is to be connected by Ethernet, you have one major hurdle - will your ISP recognize the ADSL modem connected to you?
If you are presently using a 56K modem connection to your ISP, your free ADSL modem is pretty well useless. Normally, a company that offers Cable/DSL will send you their own modem that can be programmed by them to establish the connection. It is possible for you to configure your ADSL modem to work with them if their service recognizes that modem. So, actually, your first step is to speak to your ISP to set up a Cable/DSL connection.