Be sure to start all Google Home commands with “OK Google” or “Hey Google”, then tell Google Home what you'd like it to do. 

For example: 
  • “Hey Google, watch [CBS show name] from CBS on [Chromecast Name]." 
  • “Hey Google, what's playing on CBS?”
  • (While a show is streaming) “Hey Google, next” - play next episode available in that series
  • “Hey Google, turn on closed captions." 

Happy streaming!