I got Cubase 6 (full version) and I hooked up my USB keyboard and I realized that there is a small but very nolticeable delay in input. (When I press the key down it takes a bit before I hear the sound through my headphones). Does anyone know how I could fix this?

Check your buffer size and use ASIO4ALL.

I have no idea what that means lol.

Check which audio driver you're using.

Devices > Device Setup > VST Audio System

If you're using a dedicated sound card that supports ASIO, use that.
If you don't have a dedicated sound card, you can download ASIO4ALL.

Open the Control Panel in the sub-menu below VST Audio System, and you can change the latency there.

I was using realtek but I downloaded asio4all. I have no idea its using it rght now but I installed it. I don't really know where I find the input options of drivers on cubase let alone how to set it up lol.

I think you can find it in the manual somewhere or online how to switch to ASIO.

If you increase the buffer, you get better performance, but increased latency. If you decrease the buffer, you get decreased latency, but performance drops (ie. clicks and pops, scratchy sound, hiccups, etc.; this happens when the CPU is pushed).
Secondly, just in case you don't waste any time, ASIO can run one instance at a time. If you're running another application that's using the sound driver before you launch Cubase, close those applications first because it will prevent Cubase from launching ASIO. One ASIO program at a time.

ASIO4All fixed the problem, THANK YOU!!!!

I cannot tell you how thankful I am for that. It was a 45ms output delay before but it was just enough that it bugged me and I couldn't play anything.