You take creatine on both training and rest days.
People take up to 15 grams a day. I take 5 grams pre workout and 5 grams post workout. Don't worry about the loading phase as they say that's not needed and just a waste. The duration I follow is 3 weeks on and 1 week off. Drink lots of water. This is important when taking creatine, as it takes your body's water and moves it to your muscles. This gives the illusion of having larger muscles.