You should have 3 parts: the kickstand, the top plate, and the bolt.

Find the space by the crank that is just in front of the rear tire.

Start to thread the bold through the top plate and place it across the chain stays. (the 2 bars that split off of the bottom bracket)

The plate should be centered between the rear tire and the seat tube. 
Place the kickstand underneath with the arm facing away from the frame.
Thread the bolt into the kickstand, making sure the kickstand clears the rear tire and pedals.

If the kickstand clears the tire and pedal, tighten the bolt all the way down.

Once fully tightened you should see some thread through the bottom plate.

You're now ready to use your kickstand.