Hi,
the CSL/JSON ids are in the long list here in the readme: GitHub - tropy/tropy-plugin-csl.
They represent the Zotero metadata fields. So for example if you want to map Tropy’s dc:title to Zotero’s title field, you enter title into the label of the dc:title property. To map dc:creator to Zotero’s author field, you’d enter author into the label of the dc:creator property and so on:
Be aware that you can only use ids that are available in that list and make sure to map a field (typically your dc:type field) to Zotero’s type field. Then, in your project, use valid type values for your items (e.g. manuscript) from this list : https://docs.citationstyles.org/en/1.0.1/specification.html#appendix-iii-types