It would help if you explained yourself some. Without some detail of what you are trying to put where in your underground camp it is difficult to give you any proper explanation. The only thing I can do is point out there are some restrictions on where camp equipment can be placed as regards its size, but if your problem isn't to do with that then you need to elaborate.
Your camp has three levels. The first level is 2 spaces high, the second is 3 spaces high and the third is 4 spaces high. Camp equipment comes in sizes 2, 3 and 4 spaces high, and 1, 2, and 3 spaces wide. Any piece of camp equipment you want to place in your underground has to be able to fit in any dug out space you have on a level. So you can place a piece of equipment that is 2 high on your second level, for example, because that level being 3 high will fit it, but you wouldn't be able to put a piece of camp equipment that is 3 high on your first level since that level is only 2 high. You would instead need to place that 3 high piece of camp equipment on either your second or third level, and if there isn't any available room for it there then you would either need to remove a piece of camp equipment that is already there to make room, or dig out a section or more to make room.
