How to on backlight my pc

@samseven you are not telling us what is going on with your Toshiba Tecra Z50-C. there should be nothing to be done to run your backlight on. It should come on as soon as you turn your computer on. If it doesn't, then the issue could be a failed backlight in your LCD. It could also be a failure of some components on your motherboard. To determine what is going on, you would need to measure the backlight voltage. Based on that voltage, you can determine where the error is most likely originating from.

So, at minimum we will need to hear the history of this laptop to get a feeling why the backlight is off. It is important to know if anything happened to it prior to the backlight not coming on.

After that we need to see your motherboard and we need to know the exact make and model for it. Post some well-focused pictures of it with your Question Adding images to an existing question