Hmm. Let’s tackle the sky kingdom first. Unfortunately, to have anything float in the sky that has a significant weight, it will need some sort of force keeping it up in the air. If this civilization has actual buildings, they would need something like jet packs or rocket propulsion to keep the buildings steady. There could also be big wind fans on the bottom (think helicopter blades, except not on the top). In either of these cases, I think there would need to be people in charge of monitoring and steering buildings. Because wind exists, it would be hard to keep them in the same place, so people would have to watch their trajectory at all times. I think their main focus would be keeping the buildings steady so people don’t fall down, and also keeping them moving in a steady direction and avoiding things like storms.
As for the sea kingdom...I assume the species occupying this civilization can breathe underwater? In this case, you can probably just have regular buildings, depending on how deep it is. I can see this kind of kingdom occurring in more shallow water, because the deeper you go, the more pressure there is from all the tons of water. The buildings would be attached to the bottom of the sea, but the bottom wouldn’t be too far down (you wouldn’t have a civilization in the Marianas trench, for instance, unless the species was adapted to withstand extreme pressure. If they were, though, they might not do so well above water or in shallower depths because their bodies wouldn’t be used to it). When I picture an underwater city, I picture a lot of spires and buildings made of stone. If these people can swim, you also would not need stairs, just holes between floors for people to swim inside. Gravity wouldn’t be so much of an issue, so people could scale the inside (or outside!) of high buildings very easily.