Start it at the bottom. Depending on what kind of lighting the tank it came from had, it will probably need to be acclimated to your lights. You can either start it at the bottom of your tank and slowly move it to the top over the course of a few weeks, or you can go to a hardware store and get light diffusing panels and layer them above it and remove the panels one by one so that it slowly gets more light until all the panels are gone.
How about a pic?? :D