Here’s a CODAP doc with NC census tracts.
https://codap.concord.org/releases/latest/static/dg/en/cert/index.html#shared=https%3A%2F%2Fcfm-shared.concord.org%2FrPsp6ogNPu0J6ZzzYj0p%2Ffile.json
To make this I searched the web for NC census tracts geoJSON, but could not find that. I was able to find shapefiles, which were here.
Then I opened this great tool (mapshaper.org) for simplifying and converting between various boundary file types. I uploaded the files that I had downloaded, clicked “simplify” and used the slider to reduce file size, and then “export” to save as geoJSON. Then you can just drag the geoJSON into CODAP and join tables based on one of the identifiers (assuming your data has one of those identifiers for linking).