The Luxury Bed (Black) deco is part of the Luxury Bundle, a set of decorations that you can buy directly from the Cartel Market with Cartel Coins. All decorations from the cartel market, including the Luxury Bed (Black) deco, can usually be found on the Galactic Trade Network (GTN) and bought from other players with credits.
If you're looking to get a Luxury Bed (Black), the easiest way to get it is to head to the Galactic Trade Network (GTN) in SWTOR and buy it with credits from another player. You can also buy the full Luxury Bundle from the cartel market or GTN, which includes this deco and a few others that match.
The Luxury Bed (Black) deco can also be bought straight from the Cartel Market for 110 Cartel Coins.