No CC - custom furniture

I'm trying to make a built in toddler bed. I've been watching youtube tutorials and looking for any info on how to do this. I've been trying to follow the instructions and in the videos it shows the toddlers using the objects, but when I send my toddler, they can't use the bed. It doesn't look like they're moving the bed off grid or anything that would change how it works.

Does anyone know how to do this? Can you point me to a tutorial that does more explaining?