Hi there. I was able to catch my own swarm yesterday. They have all moved into the nuc box. I have 3 frames in there and an inline feeder.
I’m not sure what to do next!
I was thinking of pulling out the inline feeder and adding a top feeder in the hole in the nuc lid and adding 2 more frames. Do I need to block them in for a few days?
If they moved into that one box, you probably caught the queen.
We usually just move them to a location in our apiary. To make sure they have enough room we move them into a new hive (one deep box or two Medium boxes with frames and feeder). An active swarm may develop fast so we try to provide enough room. Just do something similar than with a package.
We usually do not do anything else, but in some cases (around 10%) the swarm may decide to leave. They may have spotted a nice place in the wild (or inside someone's wall) and still continue the trip to that location. In nature, bee's try to propagate moving far away from their original location. So, by moving them back to the original bee yard, some colonies may decide to push away and put some distance from the original place (even if they like your accommodations - nothing personal).
To prevent losing a swarm, some beekeepers implement extra measures. The only one we like is adding a frame with brood, including larva that needs to be fed. Colonies have a hard time to leave any brood behind, so they'd be trying to stay in your hive until the brood is taken care of. After some days they usually just settle down.
Some beekeepers close the bees down (with mesh, so air can still go through the hardware) but we don't like that approach so much. The idea is that if the queen lays some eggs, they'd be forced to stay once you open up the entrance. But sometimes they're just waiting for you to open up and take off as soon as they can. They may not like being trapped in a hive and sometimes may abscond from hardware that could be harmful to them (as when there's a disease in the combs or a failed hive).
If you really want them to stay there, we recommend you to move them into their own hive (similar to a package or nuc installation), give them some syrup and add a frame with brood from another hive (it could be their original hive, making sure there are no queen cells in that brood frame).
We'd recommend making those changes by the end of the day, so they're less likely to have enough time to take off when you open them up.
They'll need some time to detect the presence of brood, so if you do it by the end of the day, they'd stay overnight and should not be thinking about leaving the brood behind tomorrow.