Like the others said.... Screw em back on and use them. If it's a true tri bike it's mean't to be very aerodynamic, and the aerobars are a part of that equation. I use my tri bike for all my races- short and long. And a short race will be perfect because your trunk and neck muscles won't be fatigued from being in them for 3+ hours. It's a great place to start.
That being said, there is a real "comfort curve" that you will have to overcome. It's a different feel in the aerobars and it takes some getting used to. not only in your body, but in the way the bike handles. So be sure to train on them.
I couldn't imagine being without my aerobars. I like to change positions frequently on long rides so having them there is just another position.