As I said I am not very computer smart, so please bear with me. First off you using a laptop or desk top? Second, are you using Windows 10.
I will speak from my point of view since I have a laptop and it shows me my laptop screen as number one, and my monitor or TV as number two.
This is Windows 10, so not sure if it will be different for you.
Go to Start and then Settings.
Go to Display.
You should see a big rectangle and a small rectangle. Click on Identify. What does it say? Since I am on the TV/monitor right now, it says number 2 for me in the bigger box. (I guess it’s bigger since I set number one to shut off.)
Scroll down. You should see multiple displays.
Then where it says Multiple displays you have 4 options. 1)Duplicate these displays. That means both screens show the same thing. 2) Extend these displays. That should make it one bigger screen. Not sure if this is your setting or not. 3)Show only on 1. 4) Show only on 2.
I still don’t know what you have or settings you have, so I am guessing here. I set my display as 2)Extend these displays to try out. (not I have the rectangles the same size since I am using extended display.
Right now, my TV says 2 and my laptop says 1. Scroll back down again where you see Multiple displays. Check on the box that says Make this my main display.
See if that works for you.
If that doesn’t work for you, I need to know what you are using, how you are using it so I cant try and help you better.
I hope this helps. Please let me know if it doesn’t work.
Scroll back up and click on the identify button.