Some helpful resources for chromecast setup.  The links are summarized below.

https://support.google.com/chromecast/answer/2998456?co=GENIE.Platform%3DDesktop&hl=en&oco=0

https://productforums.google.com/forum/#!topic/chromecast/ZGm4p8VcpAU

Set up essentials

• A display device with an HDMI input, for example, a high-definition television (HDTV)
• Access to an available power outlet or an available (non-service) USB port on your HDMI-enabled display
• Access to a secure wireless network (make sure you have the wireless network password handy)
• For Chromecast (1st generation), connection to a Wi-Fi 802.11 b/g/n 2.4G network. For Chromecast, connection to a Wi-Fi 802.11 b/g/n/ac 2.4/5G network (5G is recommended).
• A compatible Android or iOS device, or Mac, Windows or Chromebook computer (see list below). Note: The compatible Android, iOS, or tablet setup device must support a 5GHz connection in order to set up a Chromecast on a 5GHz connection.

What router settings do I need to setup Chromecast?

• Make sure your router is within 10-15 feet of your Chromecast.
• Enable: Universal Plug and Play (UPnP), multicast, Internet Group Management Protocol (IGMP)
• Disable: AP/client isolation, virtual private networks (VPNs), proxy servers, IGMP Proxy
• Please note, each router and its settings are a bit different. Contact your router manufacturer for details.
• If you’re using a BT Hub, turn off the Smart Setup feature in the router settings and reset the Chromecast. 

If you are still having problems check out the Chromecast Troubleshooter.