You have to make your request at Wikipedia:Changing username, not on your talk page, by following the instructions there.  After your username has been changed by an administrator, you will be allowed to make edits again.  If you only intend to edit a specific article or topic on Wikipedia and never anything else, then that is a single-purpose account and strongly discouraged.  If you intend to edit on a variety of articles or topics, then you are free to make contributions, and I welcome you to Wikipedia.  Please let me know if there are any more questions.
By the way, you should add four tildes ( ~~~~ ) to the end of the comments you make on talk pages.  That will add a signature with your username and the date and time you made the comment, which helps other users follow discussions.  Thanks!   talk