First off, anemones are not corals, they are mobile inverts that have different requirements then corals. The best you can do is make sure that they have good lighting, good water flow and plenty of space to move around in because they will move until they find a place to their liking; which may not be to your liking.
It's best to do some research about animals BEFORE you buy them to make sure that you will be able to provide for their proper care. Anemones generally do NOT do well in aquariums and ones that are white or close to being pure white are generally very sick or nearly dead. They are photosynthetic creatures and should have a brownish colouration to their tenticals which indicates that they still have their symbiotic algae within their flesh. Without this algae there is very little chance of survival in captivity. Once they reach this stage even with the best lighting and water conditions it's highly unlikely it'll survive for very long (MAYBE a couple months at the most).
Another thing to note about anemones is that they have a slow motabolism. This means that they can appear to survive fore many weeks before secumbing to injuries, illness or pore water conditions. It's vital that any anemone you purchase is in top condition before you purchase them as they will have the best chances of survival. If there is a tear on them,poor/white colouration or anything else that doesn't seem right then they aren't going to live.
In the wild anemones can live hundreds of years, in captivity anemones rarely live longer then 6 months! This is about how long it takes for an animal with a very slow motabolism to starve to death or secumb to any damages that occured during shipping, handling, collection or poor environment.