Make sure you’ve read the general notes about all the nodes.
This node creates several instances of the same building mesh data, places each instance in a random location on a given surface, give it a random scale, and can also give it a random rotation around the Z axis. It returns the result in the form of another mesh data.
A buildings size map can be used. The buildings placed where the map has high values will be larger. By how much depends on the size parameters. Any building built on map values below zero will be discarded.
The node can take a previous mesh data, and append its result to it. This lets you chain several different layouts for instance.
This node can take a lot of time to do its job, especially with large numbers of buildings. While it’s working, Blender is frozen. This is how Blender works and it’s unfortunately impossible for an addon to display a progress bar. But if you have the Blender console opened, this node prints its progress in it.
The size parameters should be easy to understand from their name and tooltip. But keep in mind that those are multipliers of the size of the input building mesh. Therefore if your building is 10 Blender units tall for instance, the default size values will make it very large, multiplying it by 10 or 20 at least. You should adjust the size parameters based on the size of your building mesh, and on the range of sizes you want it to have in the result.
If you use the procedural cube mesh as input building mesh data, its default size is (1,1,1), and therefore the size parameters will be the final size of the buildings.