I was told to buy a deco m4 AC1200 to extend the range of my internet provided by Virgin.

i have followed the instructions which tell mes to plug the Deco directly into the modem, it now connects fine but is obviously useless as it is next to the modem. 
 

There are no instructions on how to connect it wirelessly? If I unplug it it disconnects, surely the whole point in it is for it to connect wirelessly? 
 

Any help is appreciated!