|There are two approaches (at least to extending wifi range.|
One is to use a plug into the mains wall socket in the are to which you wish to extend the wifi coverage. This will have a couple of antennae (not always visible depending on the make/model). The device picks up the current signal and rebroadcasts it. It does depend on the stability of the current signal in order to work effectively; and they don't always...
The other is actually "fed" via cat-5/ethernet directly, or via a homeplug device (carries the home lan around the house over mains wiring). You plug the extender into a convenient wall socket and that's more or less it; although there may be a wee bit of notional setup to go through. Some if this variety include an ethernet port as well - but not all of them do,
Most homeplug systems now include in their ranges a module that will act as wifi extender too; and is obviously designed to be fully compatible with homeplug kit that follows the established specs. These module usually allow an ethernet connection too.
For stability and better quality of service/signal generally wise(r) to use a module that is fed via cat-5/ethernet cable, rather than simply hoping the wifi to wifi link will be suffice...; be it fed directly with a cable from the main router or via the homeplug (lan over mains) system.
Also one can configure just about any wifi router (whatever its age) to be an extender - again fed via cat-5/ethernet cable.
Need more input on the above approaches... post back?