Watering bromeliads should be done when the top two inches of the soil is dry - you can touch the soil with your finger to determine soil dryness.
The center of a bromeliad is called a tank, which is where it holds its water.
Here is a diagram of a bromeliad tank which might aid your understanding on how a bromeliad stores its water:
You should fill the tank in the center (with rainwater or distilled water preferably). Here is a short You Tube video so you can get a good visual on where exactly you should water your bromeliad: https://www.youtube.com/watch?v=JYtJsC6Xea0
How much water? The video above demonstrates this nicely but basically you will be fine so long as water doesn't run down the sides into the soil when you are filling the tank.
You will also need to change the water frequently, about once a week. Let the excess water drain in a drain pan or plate, and let the plant dry out before you decide to water it again.
For more information about watering bromeliad pants, please visit the following link: