While there seems to be no way to change it in the profile page, the ‘admin’ username does not appear to be hardcoded anywhere either – all other code checks for user level and not names. This means that once created, you can rename the admin user by directly altering the name in the user table with phpMyAdmin or another database modification tool.
Go into your phpmyadmin, and click on “Databases.” Then click on the name of ur database.
Click the “Browse” icon next to wp_users. Click the edit icon next to admin – should be first button on first row (like a notepad).
Change it. Go down to the bottom and click “GO.”
do you mean the admin name for WP or the admin/user for CPanel? The latter one is done by your host. For WP just find the link on CPanel admin interface where it says phpMyadmin, click and follow the instructions above.