If you’re not seeing what you expect on your projector, your monitors are probably set to extend where the projector is like a second monitor as opposed to duplicate, which is the same thing on your projector as on your screen.
First, make sure the projector is on so it is being registered by the computer as a second monitor.
To change this, right click on the desktop somewhere and on the menu that pops up select “display settings”.
On the screen that pops up, in the lower right, it probably says “Extend desktop to this display”. Click on that and select “Duplicate desktop on 1 and 2”. This will put the same thing on the projector that is on your screen.
Don’t worry that this example has 4 monitors, duplicate on 1 and 2 will put the same thing on your projector as on your screen.