I'm assuming this is your bike and you really mean that you've removed the fork from the bike as disassembling the fork isn't really something you do by mistake.
The specs I found say that you've got a threadless stem and sealed bearing headset. This is easy to reattach.
There are 3 or 4 bolts you need to be concerned with. One right at the top, that goes through a metal disc about an inch and a half wide. This is the preload bolt . Also, on your stem there will be either 2 or 3 that clamp the stem to the top of your forks.
To reassemble, find the following bits:
- 2 x sealed bearings, one for the top and one for the bottom of the head tube.
- Stem cap
- Preload blot
- Split washer (sometimes)
- Spacers (often)
Start by inserting the bearings into the cups in the top and bottom of the head tube.
Next slide the forks up through the head tube, add the split washer, spacers, stem, top cap and preload bolt. In that order.
Tighten everything down with the preload bolt so there is no unwated play. Rock the bike backward and forward, with the front brake on, and make sure there is no knocking.
When there is no play, straighten the stem and tighten the clamp bolts. Afterwards I usually loosen the preload bolt to finger tight, but some people don't.
Ta-Da! One fixed bike.