Hello Jeremy,

Your username can only be changed by an administrator,   but you can change your display name, which is what people on the support forum will see :

Click on your avatar or (current) display name at the top right of this page.

Then click on "View Profile" <big>→</big> "Edit my profile".

Then click on the blue button that says "Manage Firefox Account",   and you will see where and how to change your display name.

Can I request for an administrator to change my username? If so, how can I do so?

I will send you a PM   (Private Message).

To those of you who were not able to see what happened after that, McCoy said to send a private message to Kiki, the community admin.