Hi, welcome to Encyclopedia SpongeBobia, the wiki about SpongeBob SquarePants that anyone can edit! The reason you obtained this automated message was because you had recently made an edit to the Some Spongebob songs sound like Teen Beach Movie page.
Second, you can go up to the Avatar on your Profile Page. Then under it, click "Edit Avatar". It'll take you to a new page. Instead of the images provided by Wikia, click Upload Avatar, or Choose File on that page. Then take an image from your computer.