Let me try to answer all your questions, bear with me:
The controller of a spell is the player who cast the spell. For example, if you cast a Goblin, then you control that Goblin.
If an object you control casts a spell for you, then you are also the controller for that spell or object. For example, if your Fellela familiar casts an enchantment, then you also control that enchantment.
Sometimes, that control can change with a spell like Mind Control. If you cast a Mind Control on a creature, you now become the creature's controller, instead of the player who cast the creature.
Very importantly: The player, is represented on the board by his Mage card. So the player, and his Mage, are one and the same.
So, when you cast Mind Control, your Mage on the board controls that Mind Control enchantment. In order to reveal it, he (the Mage card on the board) must be no further than one zone away from the Mind Control spell. (We did this both for spell balance and realism). Once it is revealed, and the reveal cost is paid, you now control that creature.
I hope this answers your question and makes sense!
