Introducing a new queen to a hive can be an easy task but it can also go horribly wrong. First, the hive must be without a queen. Typically for about 24 hours would be best to go without a queen. Any longer and they will start making a new queen. Any less and they may not yet have a hive consensus that they are queenless.
There is a chance that the hive will reject the queen and kill her. In this example, the bees take to her very quickly and are not showing any signs of aggression to the new queen. The queen can be introduced immediately if the hive is not showing signs of aggression. However it is best to wait a 3 day period for her pheromones to saturate the hive.