Usually the fields are placed in template positions, via the template manager.
But besides the above, you can customize appearance of templates via their (per layout) parameters.
Every FLEXIcontent Template has 2 layouts (category and item, maybe in future we will have 'tags' too etc), each of them (category, item) defines its parameters in category.xml and item.xml files inside each template folder
These appear as a slider at bottom right corner of forms:
- category edit form (category layout)
- content type edit form (item layout)
- item edit form (item layout) (avoids this use the above)
when you select a different template layout this slider with parameters changes to reflect the parameters of the currently chosen template