After lots of maneuvering, here’s how you fix it:
- Have the external monitor plugged into your Mac.
- Go to System Preferences, select the “Displays” icon.
- There are two windows that open up (one is titled “Built-in Display” (your Mac’s screen); the other is titled “Display,” meaning: external display monitor). If you don’t see a second window, move the front window to uncover the second window.
- Get the window titled “Display” in front, and click on its “Arrangement” tab. Now you can solve the issue:
a) In “Arrangement,” each blue box represents a monitor: one blue box represents your built-in monitor (your Mac’s); the other represents your external monitor. Click and briefly hold down on one of the blue boxes: when you do this, both the blue box and the physical monitor it represents will get a red line around it. This is how you know which box in “Arrangement” is which monitor.
b) Now, you want the blue box that represents your Mac’s screen to be on top; so: click and hold (keep holding) right in the middle of the blue box that represents your Mac’s screen (when you click and hold, your physical Mac screen will have a red box on its edges), and drag the blue box so that it is directly on top of the other blue box (as you’re looking at the “Arrangements” window). Quit holding and drop it there on top. Half fixed now.
c) Next, in the ”Arrangements” window, click and hold on the white bar only (put the point of your mouse in the white bar that’s probably at the top of your top blue box (in the “Arrangements” window), and drag the white bar only (note: when you click and hold the white bar, at first the entire blue box that the white bar’s on top of will be surrounded by red. Don’t worry.) to the other (bottom) blue box (right in the center of it), and drop it there. It will snap to the top of the bottom box. Now it’s fixed—your desktop files and notifications and dock are all up on your external monitor.
So that you know what just happened: 1) The white bar represents where your main desktop and its icons (files, volumes, etc.) and notifications appear. Thus, by moving the white bar, you transferred your main desktop from your Mac screen to your external monitor (which is at the bottom in the “Arrangement” window). 2) The dock is automatically placed on monitor that is represented by the bottom blue box in the “Appearances” window. (Thus, you have to have your external monitor blue box in the bottom position in “Appearances” in order to have your dock on your external monitor. No other way to do it, unfortunately.)
