Changing restrictions passcode

When i first bought my iPhone i was just checking out the features on it when i went into the restrictions section. It asked me to set a passcode so i just put in 1234 quickly because i wanted to see what it offered. I now actually want to use that feature but obviously i need to change the passcode. I cant find anywhere that says change your passcode except for the option above in passcode lock, but this is for a different passcode altogether.

Can anyone help?