As well as the selector and your speakers you will need to have two lengths of speaker wire to connect the amplifier on your stereo to the speaker selector.
Once that is done, you just plug the wires for each pair of speakers into the back of the selector, turn the stereo back on and away you go! It works.
I can detect no loss of audio quality and the improvement provided by the additional speakers makes a real difference. A good, simple product which does what it says on the box.