If your bees have already swarmed then you have only 1 choice. You must through the colony and remove all but 1 queen cell. Leave an unsealed cell if you can as this will give you the reassurance that the developing cell is a good one with a live larvae in it. This will also give you an idea of how long to leave the colony before you can expect eggs. The new queen will emerge 8 days after the cell has been sealed and will hopefully mate successfully and start to lay anywhere between 2 to 3 weeks. I leave my colonies for 3 weeks and just keep an eye on the entrance, as soon as the new queen has completed her mating flights the bees will start to gather more pollen so by observing what is going on at the entrance you can see if all is well. Check them in around 3 weeks time and you should see some eggs. If you don’t see eggs look for polished cells as this means the queen is imminently going to start laying.
If you find that on inspection your bees have not actually swarmed, as you have just seen your marked queen in the colony, you can carry out a swarm control method, I have a separate post with a very simple method that is easy to carry out and you are likely to have equipment to do so. Artificial swarm.