Hi,
I attached some tutorial about live values. Details depend on what exactly would you like to do - to get logged in users data you can use described User live plugin.
But if your desire is to get current article author's data into form it will be more complicated, you will need to use either SD live plugin (if all needed data is already stored in article or SQL plugin (with this one you can get data from database but you need to know sql) to get needed information.