Set up user name?

How and where do I change the name under my avatar? I’ve gone to the settings and changed (and saved both window and page) the signature thinking that was the way to do it, but it still just gives my email. Or is my email visible to me only and others see my sígnature/ user name. Or is that called something else? I apologize if this is posted elsewhere, but I have searched. Thank you

Hello! I have to change your name behind the scenes. What would you like it changed to?