Hi, plug in your Ultimaker 3 to your router via an Ethernet cable. On the printer got to settings/network run down the selection and to "LAN cable". At the bottom of the screen you should see the internet address (eg 192.168.107) note this. Now go to a computer on your network and fire up a web browser and type the printer address you noted, in the address bar, which should bring up "Welcome to your Ultimaker 3" page with a start a "Start WIFI setup" button on it.