In one sentence, describe what the following article is about:

It's in the menu bar in the upper-left corner of the desktop.  This displays the Apple menu as a drop-down. It's in the Apple menu on your Mac. It's below an icon that resembles a monitor in the System Preferences menu. It's the first tab at the top of the screen. This allows you to select a screen resolution for your monitor.  By default, your MacBook will try to detect the best resolution for both your displays. To change the resolution of your MacBook display, select "Scaled" without holding the "Options" key. A higher resolution can display smaller icons and more room on the screen.  A lower resolution can display larger icons but less room on the screen.  Some apps and windows may not fit on the screen with a smaller resolution. If it's an HD monitor, select up to 1900 x 1080.  If it's a 4k or more display, select up to 3840 x 2160

Summary:
Click the Apple icon  on your MacBook. Click System Preferences. Click Displays. Click Display. Press and hold Options and select "Scaled". Select a resolution for your monitor.