Grouping Items in Boxes (PDF Editor)

I noticed some of the templates have items grouped into boxes (making it easier to move multiple items around at the same time). I haven't quite figured out how to add items into these boxes or create my own groupings. I have successfully added a few items to the box, but not consistently. 

To clarify, are you referring to the Box field in your PDF editor?

You may insert multiple fields inside to group them. You may drag and drop the fields into your Box field.

You may also edit the sizes of your fields be selecting them and resizing.

Hope this information helps.