Sometimes it is necessary to override the default settings for Joomla generated text.
The example in hand is to change the prompt for Username and Password, where we want to prompt for Email Address.
We can either edit the configuration text files (dangerous, complicated, and needs access to the data folders, and you need to know which files to edit)
…or we can do it the easy way, and change the settings from the back-end
System->Control Panel->Language Manager->Overrides
Simply create a new override, or edit one that is already set
Done!