How do I change my Username for Community?
First you need to login in to the Community with your existing username. Once you have done that, then click on your Avatar in the middle of the page ( click here to make sure you are on the home page) this is what you should see:
Click on My Settings, and you will see selection of areas to choose from, if not already displaying, click on Personal, and then change your username! You will be required to verify it is your via email, but it is that simple!!