Q: How to change Admin name in El Capitan

I would suggest reading through this carefully before changing the account name.

Change the account name and home directory name on your Mac - Apple Support

Do you actually use the account for anything productive, or is it just for doing administrative tasks?

If the latter, create a new account with the name you want and give it administrative capabilities. Then delete the original account.

I'm looking for an answer to this question too... i do not want to delete the current account just change the name, since I've been divorced, my married name is mocking me...

Chroot posted a link to the directions, above.

Following the directions posted above it tells you to open system preferences under the admin account and then right click to get a drop down menu for advanced options... only for me, the right click does nothing... I do not get a drop down menu. 

You may need to unlock the padlock first. Also, you must log in as a different admin user than the one you are changing.