change owner

You want to change the user name?

You want to make sure your name or some else's name is in your macbook?

please clarify what you want to do....

Here are the instructions from Apple on changing user short name or home directory name. I've used this on a couple of used MacBooks I've bought on eBay. And remember to go into System Preferences>Sharing and change the Computer Name in there.
http://support.apple.com/kb/HT1428