I think a little terminology and product description would go a long way to helping figure out this problem.  First, you DSL is coming into your house from your provider and terminated to a modem.  The modem is often a router as well that provides firewall/security features and converts the DSL into Ethernet format.  The router also provides addressing structure to your home network which is what ultimately allows you to use your single DSL connection for multiple devices.  A switch is simply a devices that splits and ethernet cable and allows two way communication between devises.  In the old days there were also hubs but they only allowed communication in one direction at a time was were slow.  Switches can be cascaded allowing many devices to be addressed by a single router.

The bottom line here is you need to decide how you wish to connect your devices.  Wired or Wireless?  If you go the wired route you simply need to run a single Cat5e or 6 cable from your existing modem/router to your new location.  Purchase a switch and plug in your devices.....you can get 5 to 48 port switches.  If you wish to go wireless you may want to look into a dedicated access point from Ubiquiti (nanostation, picostation, etc).  Then disable the wireless in your current router, plug in your new, more powerfull device, and go from there.

I have a Ubiquiti Nanostation on my roof and have excellent Wifi coverage in my basement 80' away.