I would get a router to put between the DSL modem and the network extender. Then you will have additional spare ports for creating/ expanding your home computer network. If you using the wireless on the DSL modem, you can turn off if you get a router with wireless built in and use the wireless from the router instead of the DSL modem.
Hope that helps.
Can anyone suggest how I connect a new network extender to a DSL modem with only one ethernet port? The phone company that provides the DSL service told me it's the only model they have that will work with our DSL service (a device with one ethernet port). Is this problem easily solved by buying a splitter? Other advice?