Yahoo! Messenger automatically looks at the first and last name in "My Contact Details" to see if you've entered a name. If you have, that name will show up to friends you send add requests to. Please note that even if you've entered your middle name it won't be shown.
If you haven't entered your first and last name, Yahoo! Messenger will look at the name from the Address/Contact Information section on your Account Info page, under "My Contact Info." If you haven't entered any information here either, your regular Yahoo! ID will show up to friends you send add requests to.
If you want to edit your name on your Account Info page, follow these simple steps: