To make Minecraft Bedrock Edition full screen on a desktop or laptop computer, you can follow these steps:
Open the game.
Click the Options button in the main menu.
In the Options menu, click the Video Settings button.
Under the "Window Mode" option, select the "Fullscreen" option.
Click the Done button to save your changes and exit the Options menu.
The game will now be in full-screen mode, and will take up the entire screen.
If you want to exit full-screen mode, you can press the Escape key on your keyboard to bring up the in-game menu, and then click the Options button and change the "Window Mode" option back to "Windowed" or "Borderless Window".
Keep in mind that the specific steps and options may vary depending on the version of Minecraft Bedrock Edition you are using and the device you are playing on.