The VIZIO M50-C1 50-Inch 4K Ultra HD Smart LED HDTV (Click here for pricing on Amazon) already has some smart TV features, but you use the Amazon Fire TV Stick to get a better overall Amazon TV experience such as Alexa voice command, games, and apps.
Amazon Fire TV Stick comes in the shape of a HDMI plugable device. You can either connect it directly to the HDMI port on the TV or using the HDMI extender accessory to any the VIZIO M50-C1 50-Inch 4K TV's HDMI 2.0 port supporting 4K@60Hz. After you plug in the Amazon Fire TV Stick, go to the inputs on your VIZIO M50-C1 50-Inch 4K TV and select the Amazon Fire TV Stick which shows up as one of the HDMI inputs.
Assuming the Amazon Fire TV Stick is already setup (see this review on how to set it up), make sure it's connected to the Internet. If you need to connect to your local WI-FI network, go to Settings -> System -> Network -> Update Connection -> select any available WI-FI Network.
Once you are connected to the Internet, you can easily browse videos from the Amazon Fire TV Stick using the Alexa voice commands through the remote.