It sounds like the backlight is bad. Usually the only option is to replace the LCD screen in the laptop.
Some older laptops have a separate little board that connects in between the LCD and the motherboard called an inverter. It provides correct power output from the motherboard to the LCD's backlight. If your laptop has one of these you can try replacing that before replacing the whole screen.
if it's a newer model, it probably doesn't have one of those in which case the whole screen must be replaced.
Best of luck to you in your studies for the A+ and welcome to the forums.