You could get a wireless dongle but "Home Plugs" would probably be better . In effect you use the house wiring. One plug goes into a mains socket near the router and connected to it by Ethernet cable (which comes with a 2 plug set) and the other plug similarly near the PC and connected to it by Ethernet cable. I bought a pair at Argos of TP Link ones (500Mbps) for £24.99. See:
Plug into mains socket, not a protected extension. Mine linked a Smart TV to the router.