If you would like to change the name displayed to the left hand side of your posts..

<-- That one over there.

Then follow this simple procedure. First of all, at the top of the web page, click on the Profile button in the menu bar. Once that has loaded you will note in the first section a field called Display Name. This is where you enter the name you wish to use on the forums. Once finished, scroll to the bottom of the screen and click "Update Registration".

Job Done.