You can change your account name by accessing your account settings. Hover over your name at the top right corner of the homepage and choose Account Settings" when the menu appears. Enter the updated account name in the "Name" field and then click "Update" to save the change.
You can also change the Sender/Host name on a per-event basis on the Add Guests/Recipients page when you're creating your guest list.
Please note that you will not be able to save account names with special characters (excluding ampersands ) or symbols.