How do i fix my macbook pro?

If you've already tried turning up the brightness of the screen (the "sun" icon), then you may have a problem with the backlight (possibly burnt out, in which case you'd need a new backlight bulb). See this post for more details:
How do fix my Macbook dark screen

Could be the inverter. If you connect an external monitor to it and it works that would be a good way to see if it is the inverter. The inverter is a ccfl cold cathode fluorescent light basically a long thin fluorescent light that illuminates the lcd. If you take a flashlight and shine it on the screen when it is on you may be able to see the computer is actually working and the lcd is ok. It is not that expensive to replace the lcd. It is however a little challenging.

ifixit.com shows step by step how to fix or repair or replace anything on the mac.

If the laptop still works you were lucky. The screen will die eventually when you open the lid too far again.
Take it to Apple and get it fixed.

just turn off your Macbook. wait in seconds and turn on.

You have a bad driver. Reinstall your screen driver or clear your P ram by holding the letters P and R and the control button when you boot your laptop. Hold them until it chimes and reboots.

I think your macbook is running on power save mode. This will turn your screen black (off) after few minutes of no interaction with the computer or if your PC is on idle.

Sorry but your lcd backlight needs replacement. Take it to the apple store and see if they'll give you a replacement. If they don't there are third party Macbook Repair services that can fix it for you. There are also free Macbook Repair guide that show you how to fix it yourself. The part is on Ebay.

try and external lcd/monitor and see how it works out for you. either a cabling issue with the lcd, the lcd, or the inverter of the screen.

is the battery fully charged? try plugging it in then press the power button again.