Your post tells me nothing about whether or not you are rooted already.
Just in case you aren't, you need
root access, and CWM installed.
I'll provide you with the links.
You'll need this tool to flash the root to your phone. It's called Odin.
Odin Flashing Utility
Now download this ROM and flash it using Odin. It will root your device:
ED01 Stock Rooted
Now, download the CWM and flash it using Odin. This is the custom recovery:
Now, with root access, and CWM installed, you should not have any problems installing a new custom ROM.
You want GummyCharged 2.0? Well just to insure that you downloaded it from the right source, I will provide a link for that too:
Again, if you are already rooted and have CWM installed, sorry for wasting your reading time. Your post just didn't give me ANY information, so I just assume that you aren't rooted.