What If I Change My Minecraft Username?
On the forum, go to your name in the top left corner and hold your cursor over it, you don't need to click.
Then click on 'Personal Details'.
Next you will see your personal details page. Scroll down, and in the menu on the left hand side you will see "Update Username' Click on this, and wait, and if you have changed your username, your forum username will change too.
If you haven't changed your Minecraft username, you will get an error, reminding you that you haven't changed your username.