You need a wireless extender kit which will give you wifi without any cables. If you google that then there'll be multiple options which come up.
I have a Devolo wifi extender and can recommend that brand. Gist is that you plug one adapter into a power skt upstairs where your router is, and then connect it to your router via ethernet lead, which comes with the kit. The other adapter then plugs into your mains power skt downstairs and forms a local network which transmits your wifi signal. In short, it uses your mains wiring to transmit the wifi signal.