There are Sooooooooo many options to do this these days.
I have a several years old LG TV and even that lets me use the TV as a 2nd screen either extended or mirrored etc via Intel WiDi.
If you have a smart TV that connects to your router/internet, it might be worth checking you can already stream straight to it without the addition of extra boxes or software, even on older devices like mine.
In Windows 10 (and 8) simply click notifications (next to the clock on the taskbar) and select 'Project'.
From the 'Project' menu you can choose how you want the Wireless display to be shown, just like any other additional monitor.
Your TV may need to be in a certain mode, my LG for example has an obvious 'Screen Share' channel.
** Additional Tips:
Always set your TV's colour scheme to 'Game Mode', as this uses less processing thus reducing lag between you pressing a button on your controller and something happening on screen.