It's really hard to explain how to properly use gears through a forum - you really need to be physically shown and you learn through riding. Bottom line you need to udnerstand the use of cadence. You should be riding comfortably at between 80 - 90 rpms and this rotation should stay the same either going uphill, down or flat. How? By using your gears. I can't tell you to stay in one gear or another to acheive this as everyone has to find their own comfort level. I might have stronger legs than you. Or you may feel more comfortable at the higher rotation, 90 rpms or more, while I'm more comfortable at 80 - 85. You should also ride with some load (ie pressure) on the pedal but not enough that you would have to push and not so light that you bounce on the saddle. Finding and using a computer that shows cadence is very helpful. If you have Shimano Ultegra or Dura Ace, I would invest in a Flightdeck comuter which shows not only cadence but your gearing as well.

What would help is if you know someone who is an experienced cyclist and ask them to take you out and provide some coaching and assistance. Doing is so much better than reading!