Left mouse button doesn't work on touchpad or usb mouse

Hello, Just got a refurbished Dell Latitude. How do you fix a problem using the keyboard commands please in order to get into mouse settings. I have tried holding the FN button and pressing every number, tried pressing ever F1 etc key..nothing. You would think I could press down the windows key but that also doesn't work. I can only move the arrow on the screen using the touchpad and right click.