I was wondering if you were using these to cycle your tank, since that seems to be what most people get damsels for... If so, please take them back to your fish store. The damsel method of cycling is outdated and rather cruel to the fish. Ammonia burns their gills and shortens their life-span.
If your tank is fully cycled, others have already noted it, but damsels get territorial and can attack other fish, often to the point of killing them. If you plan on keeping just the damsels in the tank, you'll be fine, otherwise, you might want to get them out now, or at least before you add too much live rock or other places for them to hide. They're not easy to remove once they've become accustomed to the tank.