I want to make some changes to the player houses, as I'm never happy with the ones others create. But I can't figure out how to add armor mannequins, there is nothing on the Creation Kit wiki about it. So can someone tell me, in plain English cuz I iz a noob, how I go about doing so?

I'm interested in this as well.
My understanding is the mannequin is comprised of at least two parts. One is the world object for the mannequin, the other is the activator.
I've heard you also need an X marker, but I think that may be a reference for it's location in player houses when it's swapped in when you buy the upgrade.

There's more information in this thread http://www.gamesas.com/topic/1343670-creating-new-mannequins/page__p__20256825__hl__mannequin__fromsearch__1#entry20256825

Thanks

I'm all ready for a new Bethesda tutorial video containing creating a new mannequin, weapon plaque and bookcase, hint hint

AFAIK:
The linked refs also serve to make the reference a persistent one (Persist Location column= (all) ). That means it doesn't get rebuilt / repositioned when the cell is reloaded. I think you could add a self ref link on the mannequin actor to achieve the same result.

The trigger is a bounding box around the mannequin that accepts the player activation request "'E' - Activate Mannequin", which then activates the mannequin inventory from the actor.

I'm still struggling to work out the exact sequence though to create a new one, rather than a copy of an existing one.

I had this problem, there's no way I can find to make it work without copying one of the parts. There's three parts by the way, MannequinActivateTrig, XMarkerHeading and the Mannequin. Copy the Trig from proud spire basemant (it's the smaller red box inside the XMarker) and get yourself the other two pieces from the object menu. Link ref the XMarker to the Mannequin and then do the same in reverse, linking the mannequin back to the XMarker. Then make the Trig the mannequins parent, under active parents, and click the checkbox ( I think it says parent activate only, or something like that). Now save and enjoy!