What you are looking for is Registering components by conventions. Basically what you do is that you declare what implementations Castle should consider, and what services it should associate those implementations with.
container.Register(
// we want all concrete classes in this assembly
Classes.FromThisAssembly()
// but we filter them to keep only the ones in a specific namespace
.InSameNamespaceAs<RootComponent>()
// we register thoses classes to interfaces that match the classes names
.WithService.DefaultInterfaces()
// setting the lifestyles for all components in this batch
.LifestyleTransient()
);
There are many other options for convention-based registration, the best way is to take a longer look at the linked page.