When placing a lot, it will ask you if you want it furnished or unfurnished. If you are on a lot, this will be a pop-up dialog. If you are in World view, this will be a drop-down menu. From World View From within a lot Provided that you have installed any required CC prior t...
There is an issue with certain Gallery lots where placing them furnished will crash or freeze the game every time, but that is of course not the only reason Sims 4 can crash in build mode. If you use mods or custom content, please test entirely without them, as in, move the Mods ...