My RAM is downclocked?

I built a new system last month (i5 3570k, 8GB 1600mhz RAM, Gigabyte Z77-D3H, GTX 650ti, 500w PSU, 60GB SSD and 2TB HDD..) and I have just noticed that my RAM is only running at 1333mhz. How do I change this to the 1600mhz it should be running at? I know it's something to do with the BIOS, but I'm new to messing around with hardware, and have no idea how to do it, and really don't want to f*** it up..

 

Thanks all

See if you can set your Motherboard to have the RAM run in X.M.P profile the same thing happen to my system until I dug around in it.

I had a look and found it was disabled. I enabled it to profile 1 (which it gave me) and now I am running at 1600mhz. Thanks man :)