Chrome cast help please

[#1]

i have tried to install chrome cast but it is saying the router is not allowing it to connect,now
please understand I need an idiot guide please of how to solve this many thanks in advance

[#2]

The Chromecast works with the router that you have, so I can't think of any reason why yours isn't working.
What's the exact error message that you get? Do you have the same problems on all machines or just one?
The router should work without any changes to settings.
Tony