[MainStreet, USA]

Open your User Control Panel by clicking on the "User CP" button on the left side of the topmost red bar along the top of the screen. You should see a vertical blue menu down the left side of the screen under that. The third option down should be "edit profile". Click on that and in the second box down, under the header "Optional Information" should be the sub-header "Custom User Title", which is I believe what you are looking for. There should be a box there for you to enter what you want displayed under your username.