how do i drain and refill my coolant system

Make sure the engine is cool so you don’t burn yourself. Remove the radiator cap. Then look on the bottom of the radiator in the corner. Most likely the driver’s side and there will be a drain valve. Gently twist counter clockwise and some you have to gently pull out a little at the same time. Once it has stopped draining then I have also attached the proper way to service. Make sure you use a 50/50 mix of the correct antifreeze. If you wanted to take it another step, here is a link to flushing.
http://www.youtube.com/watch?v=i36pDzhFkBQ

Some more information for you for your review

https://www.2carpros.com/articles/how-to-replace-a-car-radiator