The original poster:
How do I change owner's name? Just bought macbook pro off my son and want to put my name on the computer instead of his. please help.
asked about changing the name in the menu bar. THe comments that followed suggested two main options:
1) Changing the actual computer name, which requires changing the home directory. These comments often referenced this page from Apple: Change your OS X account name and home directory name - Apple Support
2) Changing the "Sharing" name
If 2) is NOT what you are after, then just a shout-out that for Yosemite at least the comments provided re: 1) are incorrect. You don't have to change the computer name / home directory (which I would advise against for the reasons provided) in order to change the name appearing in the top menu bar and at logon. You just have to change "Full Name" (and NOTHING ELSE) as per the process described in Change your OS X account name and home directory name - Apple Support
As the documentation shows, changing Full Name does not have the risks associated with changing the account name / home directory.
I have just changed Full Name (in Yosemite) and it is a 5-second job. The name in the menu bar updated immediately. My login initially still showed the old name, but as soon as I restarted my computer it updated.