Go to this site to learn more about the Heinie kegs:
http://www.popularmechanics.com/blogs/technology_news/4217337.html
If you really want to use mini's then look for the tap on the bottom and the black rubber bung with the red plastic "knob" (or "key" for lack of a better term). These are called gravity kegs.
You prime them with 2 TBS Corn Sugar and let them sit for a couple of weeks to condition.
To use, you open the top bung (turn red key) SLOWLY, pull out the bottom tap and turn it to dispense.
If you do not open the bung then you will create a vacuum inside the keg and it will stop dispensing.