Hardwire from Nighthawk Mesh Router to Nighthawk ax6000 extender

I have just purchased  an EX8 8 stream wifi mech extender ax6000. I would like to hard wire it from my Nighthawk Mesh router. 

Is this doable, and how would I proceed? I need to hard wire because my room has metal and plaster walls, and acts like a faraday room. I have a satellite in my room, but it does not help. I get 400 by the router and 10-15 in the room.