How to use a teleprompter on a laptop
Put the laptop at eye height, sit far enough that you can still see the type without leaning, and press full screen. Space starts and stops the scroll so you do not have to hunt for a button while you talk.
If you record with the laptop webcam, the audience will see your eyes drift if the type is too small or the speed is too high. Raise the type until you can read a line without scanning left and right, then slow the speed until you are waiting for the line, not chasing it. A second display — a tablet in front of the camera, or a monitor behind the lens — is kinder than reading off the same screen you are recording from.