When you're editing a document, the right-hand column will show you the Properties tab.
Here, you will be able to select an asset and view which rules have been set up for fields in this asset.
You can also see here a document overview: you will be able to see the number of assets currently in the document, and any additional assets you have inserted into the document that weren't contained in the original template (temporary assets).
You can create new temporary assets within the document (see text editor article). These new temporary assets can be saved to the Library for use in future documents.