Currently for uploading artifacts (results of an observation) in DB you need to use SIDS protocol (pdf for SIDS documentation).
You can take a look here for how SatNOGS Network implements it in order to push demodulated frames to DB.
If you want to test your software, please use the dev instance of DB at https://db-dev.satongs.org.
EDIT: About DB API documentation there is an ongoing attempt to write it (and automatically generated). You can see the results at https://docs.satnogs.org/projects/satnogs-db/en/stable/api.html.