There are some good tutorials on the forum for creating places. I would make sure that you have enough activity on your iNat account to do so, and then you can create the place.
https://forum.inaturalist.org/t/how-to-make-a-project-for-a-specific-place/41066
https://forum.inaturalist.org/t/how-to-import-a-place-from-openstreetmap-into-inaturalist-using-overpassturbo-web-based/41046
https://forum.inaturalist.org/t/how-to-import-a-place-from-openstreetmap-into-inaturalist-using-qgis-and-quickosm/41014
https://forum.inaturalist.org/t/how-to-draw-a-new-place-in-google-mymaps-for-uploading-to-inaturalist/41063
If you run into any specific issues, you can post questions on the forum and on those specific tutorials if relevant.