How can I enter the Four-Digit code on AppleTV device if I haven't a controller to access to the the settings?!?

No, it says to enter the 4-digit code on your iOS device.

Here are the instructions again.

1. Make sure that your iOS device is on the same Wi-Fi network as your Apple TV.
2. Add the Apple TV Remote to Control Center, then open Control Center.
3. Tap, then choose your Apple TV.
4. If asked, enter the four-digit code on your iOS device that appears on your Apple TV.

If your original Apple TV remote control no longer works use the instructions on this Apple support page to set up your iOS device to control your Apple TV.

https://support.apple.com/en-ca/HT208492

I see what you mean. I can also see the screen of your Apple TV in the background and was wondering if the problem you are having is because the model of Apple TV you have is too old for this to work. The Apple support page mentions Apple TV models 3rd generation and newer. If your Apple TV is older then the behaviour might be different.