Getting the most out of my gaming PC??

Hey fellow vergers... I need some help getting the most out of my new gaming PC. So I've always been a console gamer first but I've decided to give the PC a chance, especially since I've recently discovered the steam deals (I know I'm a bit late on this...)

Here's the thing- I know a lot of people get mad about these things but I bought an Alienware X51. I am fully aware that I could've built a much more powerful machine for less money, but like I said, I'm new and just wanted something that would come working out of the box. So I took the easy road out. I don't need to play Crysis on Ultra 1080p, BUT here is my issue:

My PC seems like it should be performing way better than it is.

Core i7

8GB GDDR3

NVIDIA GTX 760 ( I know this card is somewhat compromised to fit into the Alienware case)

Anyways, here is my problem:

I can barely run Far Cry 3 on medium-low settings on 1300x768? (Something like that, I didn't want to boot up the game just to see what the resolution was.)

Is my PC really not capable of playing Far Cry 3 smoothly? Is there something I need to do to fix this? Everygame I've played so far I've had to turn way down and play on a low resolution even though I just bought this beautiful 1080p LG monitor!

I'm not trying to start any ways, I'm just seeking some help. Like I said, I'm new to the gaming PC and really am hoping I can get more out of this pc.

Thanks for the help!