Connect and arrange a second monitor so you can spread your work across two screens.
Use whatever ports match: HDMI, DisplayPort, or USB-C. Connect the cable to both the monitor and your computer, then turn the monitor on and select its input source if it doesn't detect the signal automatically.
On Windows, right-click the desktop > "Display settings." On Mac, go to System Settings > Displays. You should see two numbered rectangles representing your screens.
On Windows, set "Multiple displays" to "Extend these displays." On Mac, make sure "Mirror Displays" is unchecked. Extend lets you drag windows across; mirror just clones the same image.
Click and drag the numbered rectangles so they sit side by side the way the monitors actually are on your desk. This makes your mouse cross between screens in the right direction. Set your main screen with "Use as main display."