This is gonna sound wierd but its a 'bad ending' scenario so not posed as a good outcome

Player being forced to wear clown get up on face neck, and rest of body.

I have the objects set to wearable, but how do i script them being put on as result of npc interaction?

How can i make them un-removable?

I have the objects set to wearable, but how do i script them being put on as result of npc interaction?

WearGarment (clown mask)

(or whatever the object's actual name is)

Note that this will not check if the player actually can wear the item, it will just make it happen; so using this function could end up with the player wearing two hats at the same time, for example. If you want to remove other items from the same slot, you would need to check that first by doing something like:

while (not GetBoolean (clown mask, "worn")) {
  blocking_item = _GetOuterForGarment(game.pov, clown mask)
  if (blocking_item = null) {
    WearGarment (clown mask)
  }
  else {
    RemoveGarment (blocking_item)
  }
}

How can i make them un-removable?

If you enable "Show advanced options for wearables" on the game's 'Features' tab, the wearable rab will contain a "Removeable?" checkbox which you can turn off.

'While' then 'if'...
And the script calls each "Garment' instead of 'wearable'...

Thanks ill try those out.

How do i use the Wear Slot option? I try inputing 'face' but nothing is added to the menu.

How do i use the Wear Slot option?

It doesn't display the slot anywhere; but if the player tries to wear something when they're already wearing something in the same slot and layer, it won't let them.