From EverQuest.com, top right of the screen (Sign In or Join Free), you get this page
when you click 'Sign In'
When you sign in there, then click your username (same spot where the 'Sign In or Join Free' link was), you get the account management screen. Second from the bottom is 'Enter Activation Code'.
Now, given the number of accounts I have, I have the sign-in screen bookmarked so I just hit it in my links bar in Chrome and it takes me right to the sign-in screen.