Introducing virgin queens can be tricky, but we have been very successful using an introduction method developed by Cory Stevens from Stevens Bee Company. (Special thanks for compiling this FAQ by Matthew Kobe at Kobe Apiaries)
1. Remove the queen from the hive which you want to requeen.
2. Return to the colony in 8-9 days and remove all queen cells that the colony has started. This will make the colony hopelessly queenless as they do not have any young larva to develop a queen from. Be sure to shake or brush the bees off of the frames to ensure you do not miss any queen cells. If you miss even one cell, it is likely that the bees will kill the virgin queen you are trying to introduce to them.
3. Add the virgin queen in a candy cage. You can choose to tape over the candy plug to extend the amount of time it takes for the bees to release the virgin queen.
4. Check back in 3-5 days to ensure that the queen was released from the candy cage. If she has not been released, manually release her into the colony.
5. Check back in 2-3 weeks for a mated queen. Do not check back too early as this can trigger the colony to kill the young queen.