How do I supply local source to project.yml

[remmi11]

How do I combine local and remote sources in mapbox studio. Do I need to upload data to mapbox or can i do this all locally? After I save a style (tm2) I can edit its project.yml to point at sources. Can I include local source and if what is the correct syntax. Here is what I am trying. It returns server error (400).

inside project.yml
source: "mapbox:///mapbox.mapbox-terrain-v2,mapbox.mapbox-streets-v6,tmsource://c:/Users/wtgeo_000/Desktop/final/Data/country_names_all_sizes.tm2source,<map id>,<map id>"

What is the correct way of doing this?