あたらし(= 新) is a relatively common Japanese surname, so 私はあたらしです actually means "My name is Atarashi". "New" is あたらしい in Japanese, but you need to say 新人です, 初めて投稿します or like that for "I'm new". Please post in the Learning Japanese Section if you have further questions about this or also other things about the language. Welcome to JREF!