How can i get a water flower at home or garden?
I am assuming you mean an aquatic plant like lotus or water lily. If that's the case, you need a container that holds water, so it will grow. You can use anything from a bucket to a decorative pot. Put in mosquito dunks or mosquito fish in the container to avoid mosquitoes breeding in the stagnant water.
By water flower, you mean a water lily, or water hyacinth, or the like? You can make a small water garden yourself by making a small pond, or even lining a half barrel, or other large container, and making a small container water garden. The garden center near me stocks water garden plants starting around May 1st (too cold right now), but if you live someplace warm, you may be able to find them earlier. You can also mail order online, as water lilies can be shipped dormant very easily.