First head to async.art, once you're logged in click your name in the upper-right to reveal the dropdown menu and select "Your Profile"
Once on your profile page you'll see "Edit Account" below your username on the left. Click this to edit your account details. Here you can change your Avatar, Email, Name, Username, Social handles, and more.
Name is what you will see across the site as your main name. There can be two accounts with the same name.
Username is your unique handle. There cannot be two accounts with the same username.