Menu options have changed slightly since Year 12. The crucial thing is that the tag of the fitout needs to be exactly the same as the tag of the NPCs. To simplify the explanation, there are three steps:
First, create the desired template in the "NPC Control" menu. The name of the template automatically becomes the tag for the fitout. Drag the image of the item(s) to the image of the body.
Second, in your inventory, under "NPCs," select the desired NPCs. Assign them a tag with the exact same name as the tag of the fitout from step 1.
Third, you need to be in the same room as the fitout items and tagged NPCs. In your "Party" menu, select the tagged NPCs. After you've clicked on the white boxes to the right of their names, then on the "Actions" menu on the bottom of the page, select "Fitout: Pickup Only."
That should equip the tagged NPCs with the fitout items. If it doesn't, you need to specify which step didn't work.