Help on the keyboard.?

I got this book that teaches you how to teach yourself to play piano. It numbers your fingers 1,2,3,4, and 5. It tells me to place my thumb on C, my index finger on D, my middle finger on E, my ring finger on F, and my pinkie on G. This is with my right hand. They don't tell me what fingers to use to hit the upper C, B, and A. Could anyone give me some tips on how to move my hand or place it so i can get these notes easily?