How to activate Facetime on my iPhone?

I bought an iPhone a few days ago and I now want to use facetime but i don't know if it's an app or what? I'm confused and i don't know how to get it activated or working.

I was confused when i got mine after upgrading from my ipod touch… The touch has a facetime app that comes with it… But the iphone doesn't… And i soon discovered that it was built into the phone app… Any contacts you have (be it emails or numbers) connected to an apple device (that has a camera) you can call on facetime… You should click on the contact and it should have "facetime" as an option…

hope this helped,
chidchilli