Oh my, what was I thinking??? Thank you so much for your replies.
I forgot the most important word - locking! There are two locking casters, the rest are plain casters. My question should have been, "Where do the locking casters go?"
I suspect my brain isn't working; this move has been stressful and my primary source of relaxation has been unavailable. Many thanks for your indulgence.
Cathy (also forgot to sign the first time) 🙄