These are 6 simple steps to enable Night Light, or what you usually call Blue Light Filter, as a built-in solution to F.Lux (https://justgetflux.com/):
Open settings
Press start, then press the gear icon (settings) or press win+I
The settings window will pop up:
Navigating to the setting
Press system
It will open the “Display” sub-menu by default, as it is the first option.
Press the toggle button to switch it on
Adjust the settings by pressing the “Night light settings” text
You can set the schedule and the strength here, as well as manually turning it on and off. But you can also turn it on and off manually via the “Settings-Display“ page.
And that’s how you Enable Night Light in Windows 10, without additional third-party software!
Hope this helps!