Iain;
Here’s a Word document containing screenshot of a DFFS form that uses side-by-side settings, and a screenshot of the settings. Hopefully that will get you started. If the side-by-side “Index” box in the tab settings for a field has nothing in it, side by side is not in effect for that field. Fields with matching entries in the side-by-side “Index” box will be placed on the same line on the form.
Good luck.