Install a second-screen app on your Samsung phone, such as SuperDisplay, spacedesk, Duet Display, or Samsung Flow
Install the matching app or driver on your computer
Connect the phone and computer with a USB cable or the same Wi-Fi network
Enable Developer Options on the Samsung phone if required
Turn on USB debugging if the app requires it
Open the app on both devices
Select Extend Display or Second Screen mode
Adjust display settings on the computer to extend the desktop
Set the phone orientation to landscape
Change resolution and refresh rate in the app settings if needed
Use a phone stand or mount for better positioning
Keep the phone charged during use
Disconnect the app when finished