Computer screen doesn't project onto wall

There is a function f-key combo that you need to toggle on your laptop. I'm assuming that you are just using a laptop. Depending on the manufacturer, the f-key will have either a square with a line beside either side. Maybe it says ctr/lcd, or it looks like two squares side by side. You will have to press the fn key at the same time as the corresponding f-key, up to three times, depending on manufacturer.