Hi, and welcome. Really quickly; your poinsettia should maintain a good appearance for at least a month, perhaps longer. Water as you would other houseplants, thoroughly but infrequently as it probably is in a peat based soil. After the bracts (not flowers) begin to fade, begin to withhold water. After a brief dormancy the plant will do well outside until fall.
I recently responded to another question regarding poinsettias, look [url=https://www.helpfulgardener.com/forum/viewtopic.php?t=6800]here.[/url] Make sure to follow the links referenced in that thread. This is a little tricky and although it can be done my results have been less than spectacular.