Using a 47LG50 TV as a 3rd monitor?

Hello, everyone.
I have a late 2014 2.6 GHz Dual Intel Core Mac Mini running OS 10.13.3 High Sierra.
I am currently using a 20” HP S2031 display as my main monitor (looks just like this: https://az816207.vo.msecnd.net/photos/f9a06191-3f86-4fac-bd74-ab01c201465c.jpg) and it is connected to the Mini via the Mini’s HDMI slot (Mini's back panel here: https://support.apple.com/library/APPLE/APPLECARE_ALLGEOS/SP710/SP710-connection s_ports.jpg).
Then I have a 19” Dell 1909W display in another room (looks like this: https://images-na.ssl-images-amazon.com/images/I/41ygyqw5XIL._SL500_AC_SS350_.jp g) connected to the Mini as well via one of the Mini’s two Thunderbolt 2 slots.
The two displays are in mirror mode and show the same image.

I just recently obtained a massive 47 inch 47LG50 HD tv (looks like: https://i.ytimg.com/vi/zMxr76aoilQ/maxresdefault.jpg) and am attempting to use it as an adjacent, side by side monitor to the main HP S2031.
I purchased a Thunderbolt-to-HDMI cable and connected the cable to the second/last remaining Thunderbolt 2 slot in the Mini, and then connected the HDMI end of the cable to an “HDMI 2” slot in the back of the 47LG50.

Thus far I haven’t been able to figure out how to get the 47LG50 to display any image from the Mac Mini.
A “No Signal” icon slowly floats about the 47LG50’s screen.
When I go to the Display settings in the Mini’s System Preferences, I see an area that says “AirPlay Display” and the drop down menu has two options: A “Great Room Apple TV” option, and a “Bedroom Apple TV (3)” option.
When I click on the “Great Room Apple TV” option, the message that comes back is “Could not connect to ‘Great Room Apple TV’”.
When I click on the “Bedroom Apple TV (3)” option, the message that comes back is “Unable to connect to “Bedroom Apple TV (3)” because the wireless signal is too weak.”

I’m at a bit of a loss at this point as to how to use this 47LG50 as a display.

Any help would be greatly appreciated.

Thanks very much in advance,

Javier