Steps to change your display name on Google Plus Profile.
STEP #1 : First of all just open plus.google.com and log in with your Google Account.
STEP #2 : Now, go to your Google plus profile by moving the cursor to the Home buttonand choose Profile from the drop down list.
STEP #3 : In your Google Plus Profile, Click on your display name to edit it. For help, see the image below.
STEP #4 : And finally when you click on your display name, you’ll see the option to edit your name. As shown below, just edit your name and click on Save button to save your changes.