Congrats on taking 2nd. That's how you get hooked on mtt.
Without seeing how you played, it would be hard to say how you could or should improve. There are plenty of other threads about heads up play, and plenty of stuff to read about it.
I would recommend going to youtube and watching some heads up poker. Watch some heads up tournaments and some final table heads up play. Watch what they do and compare it to what you were doing, and see where you went wrong and where you went right. Take the areas where you went wrong and think of ways to do them differently, if possible.
Also, you could practice by playing a few more heads up SNG. I'm not a big fan of them, but they are good for the practice. Heads up is a strange and often tricky form to play. You just need some more experience to gain some more confidence in your heads up game, then you will start taking down more tournaments and SNGs.
Some advice I can give from how I play heads up: Play more
hands; widen your range considerably. Anything suited, and any two face cards are like gold. But don't be afraid to play hands like 37 off suit, or J2 off suit. These might be hands you would only rarely ever play, perhaps only when defending blinds, but in heads up the whole cliche of "you play the opponents, not the cards" rings true more so than anywhere else in the game. Don't be afraid to
bluff if you see an opportunity, but be careful not to bluff right into the nuts or fall into traps like that.
It just takes more practice. Just stick with it and keep trying to improve.