Can you be a little more specific as to what you mean by "an Amazon Fire TV"? Who makes it? What size? Do you know a specific model number (for example, 32LF221U19, which is a Toshiba 32")?
I am assuming it has at least one HDMI input in the back. Get an HDMI cable, plug one end into your Comcast cable box's output, and the other end into one of the TV's HDMI inputs; then, using the TV's remote, change the TV's input to whichever HDMI input you plugged the cable into.
Any ideas why I pay an Outrageous amount per month for Xfinity and can’t even get my service on my new tv?
New tv is an amazon fire tv, and Comcast channels won’t even scan. All your support techs on the 800 number can saw is maybe get a streaming device to get my channels. I don’t want to stream anything, I want to watch the cable I pay for, shouldn’t be this difficult
You need to read the instructions on how to set up your Fire TV. Read them carefully and follow them exactly. I have a Fire TV stick and had problems setting up until I read and followed the directions exactly.
And, as was pointed out, you need a cable box as well in order to use your Fire TV.
Your fire tv can likely be set up to allow for you to stream many many different applications which are available from Amazon. You will need the internet to access those apps. Your Comcast service is totally different. As was already pointed out, you need to plug in your cable box (which is required in order to receive cable programming). If you have a HDMI connection on your tv, plug a HDMI cable into the output of the cable box on one end and into the tv HDMI input on the other end. Of course your cable must be plugged into the cable box as well. Your service will then require activation by following directions from your cable company. HDMI will give you the best picture, that is, high definition and ultra high definition, if your tv has that capability. You can also ask the cable company to send someone to your home to connect and activate everything but that option may cost extra.