Referencing plugin code in my class + Using components

OK, I’m completely new to UE, so know basically nothing, so don’t shoot me. The question is - if I have my own class that inherits from AActor and I want a few components in it:

USkeletalMeshComponent
UGroomComponent

My USkeletalMeshComponent works ok and shows in the panel in UE editor.

The first question is - how does the editor know there’s such component in my class? Is it because I set it as the RootComponent in my class constructor?

The second question is - how do I get headers for UGroomComponent into my project? And if I get them - will it be enough to compile it? I guess not…

And the last one - since I can have a lot of components in my AActor how can I make them visible inside UE editor pane under my AActor derived class instance? Is this what UPROPERTY does automagically?

Edit: I’ve added

	PublicDependencyModuleNames.AddRange(new string[] { "HairStrandsCore", "HairStrandsEditor" });

to my project.Build.cs, but still - I have no idea how do I include these headers…