First, retrieve the SlimeWorldManager plugin API:
SlimePlugin plugin = (SlimePlugin) Bukkit.getPluginManager().getPlugin("SlimeWorldManager");
Now, you need a loader. A SlimeLoader is a class that reads and stores worlds from a data source. In this case, we'll be using the MySQL loader:
SlimeLoader sqlLoader = plugin.getLoader("mysql");
Before actually loading the world, you need a SlimePropertyMap Object. Check the property API documentation for further details.
That's it, you've got everything you need! Now, let's load the world from the data source and generate it:
try {
// note that this method should be called asynchronously
SlimeWorld world = plugin.loadWorld(sqlLoader, "my-world", props);
// note that this method must be called synchronously
plugin.loadWorld(world);
} catch (UnknownWorldException | IOException | CorruptedWorldException | NewerFormatException | WorldInUseException | UnsupportedWorldException exception) {
// exception handling
}