Hi shadon... I had real trouble cause people would talk to me about getting into little gears for this, cogs that, big chain ring for the other damned thing...

It wasn't til I was out riding and watched the big cogs at the front... the ones closest to the pedals... closest to the front of the bike. I have two cogs at the front - you may have three...

If you remember that the biggest cog is for the most effort (like thrashing along flats)...
Huge = Hard
The little cog is for least resistance (up hills, or spinning)
Little = Low

As for the back set of cogs, your chain should ideally be sitting somewhere in the middle when you change between the 2-3 cogs at the front...

Good luck - read these links the girls have posted, and practice - before long it'll be second-nature.